Exercises found in standard composition (5)
I believe the answer is:
paper
'composition' is the definition.
(academic composition)
'exercises found in standard' is the wordplay.
'exercises' becomes 'pe' (Physical Education class).
'found in' is an insertion indicator.
'standard' becomes 'par' (standard of play in golf).
'pe' going within 'par' is 'PAPER'.
(Other definitions for paper that I've seen before include "News medium" , "Telegraph, for example" , "Writing sheet(s)?" , "Set of written exam questions" , "Maybe Times" .)