Forte had put Latics ahead on 48 minutes from the penalty spot as Danny Philliskirk was fouled but Clucas' goal eight minutes later sealed a point for both sides.
The game started at a frantic pace with the game living up to the pre-match hype. Both sides looked to attack from the get-go.
Winchester was the first to test Tommy Lee from distance. The midfielder raced away with only five minutes on the clock and forced the goalkeeper into a smart save.
Minutes later, Brian Wilson picked up a booking for holding back Daniel Johnson as the forward broke from midfield.
Chesterfield, who started the game in the play off spots, had their first opportunity of the game on ten minutes. Gary Roberts' pinpoint cross found the head of the onrushing Ian Evatt but the defender saw his header go wide.
Both sides were enjoying good spells of possession but both goalkeepers were in form.
Dominic Poleon, whose pace and power was causing the Spireites defenders problems, went close mid way through the half. The midfielder travelled over 50 metres with the ball before smashing goal wards but Lee again pulled off a save.
The home side were starting to up the pressure on Latics. Jimmy Ryan thundered an effort at goal on the half hour mark but Paul Rachubka saved the shot well.
Five minutes before the break, Latics top scorer Jonathan Forte skimmed inside Tendayi Darikwa but curled his effort over the bar.
Latics almost took the lead a minute after the break. Joseph Mills' cross found the head of Poleon but the striker could not direct it on target.
The visitors did not rue that chance as they took the lead on 47 minutes. Philliskirk was fouled in the box by Georg Margrietter and Forte slammed the penalty down the middle to give Latics the lead.
That lead lasted eight minutes as the Spireites equalised. Roberts' ball over the top found Clucas and the forward volleyed home from eight yards to get Chesterfield back into the game.
The momentum was with the home side but the visitors defended resolutely with James Wilson and Timothee Dieng standing firm.
Latics made a substitution as they looked to regain the lead with Jabo Ibehre replacing Dominic Poleon.
The striker was causing a threat in attack, holding up the ball and bringing others into play.
With both sides looking for the winning goal, the game was finely poised going into the final ten minutes of the game.
Chesterfield had their a chance on 88 minutes but Samy Morsy's shot was tipped behind the post by Rachubka.
Latics almost clinched the game in the final seconds of the game. Wilson's shot caused an almighty scramble in the area but Forte could not manage to poke the ball over the line and Latics had to settle for a point.
Chesterfield: Lee, Evatt, Darikwa, Ryan, Johnson (Gardner 88'), Jones (Gnanduillet 67'), Margreitter, Clucas, Morsy, Roberts (O'Shea 85'), Doyle.
Subs not used: Hunt, Raglan, Banks, Boco.
Oldham Athletic: Rachubka, B.Wilson (Kusunga 90'), J.Wilson, Dieng, Mills, Kelly, Jones, Winchester (Dayton 73'), Forte, Philliskirk, Poleon (Ibehre 64').
Subs not used: Coleman, Brown, Tidser, Turner.
Goals: Chesterfield (Clucas 56') 1-1 Oldham Athletic (Forte 48')
Attendance: 7,130 (1,028 visiting supporters)