Organised PE? I must, creating incentive (7)
I believe the answer is:
impetus
'incentive' is the definition.
(thesaurus)
'organised pe? i must' is the wordplay.
'organised' indicates anagramming the letters.
'pe'+'i'+'must'='peimust'
'peimust' anagrammed gives 'IMPETUS'.
'creating' is the link.
(Other definitions for impetus that I've seen before include "Driving force, momentum" , "Imputes to force with which a body moves" , "Moving force" , "Incentive - time's up (anag)" , "Driving force, forward movement" .)