Pointless blowing top about one's exploit (7)
I believe the answer is:
utilise
'exploit' is the definition.
('exploit'->'utilize' is in my internal thesaurus and 'ize'->'ise')
'pointless blowing top about one's' is the wordplay.
'pointless' becomes 'futile' (I've seen this before).
'blowing top' means to remove the first letter.
'about' indicates putting letters inside.
'one's' becomes 'is' (Roman numeral).
'futile' with its initial letter taken away is 'utile'.
'utile' placed around 'is' is 'UTILISE'.
(Other definitions for utilise that I've seen before include "Employ, make use of" , "Employ, do something with" , "Put to use" , "Find application or task for" , "Put into service, find application for" .)