Pointless to exploit fewer (7)
I believe the answer is:
useless
'pointless' is the definition.
(synonyms)
'exploit fewer' is the wordplay.
'exploit' becomes 'use' (use is a kind of exploit).
'fewer' becomes 'less' (associated in meaning).
'use'+'less'='USELESS'
'to' is the link.
(Other definitions for useless that I've seen before include "Unemployable" , "Good for nothing" , "Having no beneficial function" , "Poor" , "Ineffective" .)