Sharp exercise needs web classification (11)
I believe the answer is:
penetrating
'sharp' is the definition.
('penetrating' can be a synonym of 'sharp')
'exercise needs web classification' is the wordplay.
'exercise' becomes 'pe' (Physical Education).
'needs' means one lot of letters go next to another.
'web' becomes 'net' ('net' can be a synonym of 'web').
'classification' becomes 'rating' (rating is a kind of classification**).
'pe'+'net'+'rating'='PENETRATING'
(Other definitions for penetrating that I've seen before include "Boring - keen" , "Going through" , "Acute" , "Incisive" .)