This compiler's exercise does, oddly, hinder (6)
I believe the answer is:
impede
'hinder' is the definition.
('impede' can be a synonym of 'hinder')
'this compiler's exercise does oddly' is the wordplay.
'this compiler's' becomes 'im' (I've seen this in other clues).
'exercise' becomes 'pe' (Physical Education).
'oddly' means one should take alternating letters.
The alternate letters of 'does' are 'de'.
'im'+'pe'+'de'='IMPEDE'
(Other definitions for impede that I've seen before include "check" , "Block progress of (something)" , "Cramp" , "Stand in the way of progress" , "Bar" .)