Hunter in exploit over enormously long period (7)
I believe the answer is:
actaeon
'hunter' is the definition.
(I've seen this before)
'exploit over enormously long period' is the wordplay.
'exploit over enormously' becomes 'acta' (I can't explain this - if you can you should believe this answer much more).
'long period' becomes 'eon' (I've seen this before).
'acta'+'eon'='ACTAEON'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for actaeon that I've seen before include "Old Greek hunter" , "Artemis changed him to a stag; at once a (anag.)" , "Hunter who was turned into a stag" , "Hunter who transformed" , "Hunter changed into a stag" .)