Mole inhabiting drains I'd eradicated (7)
I believe the answer is:
insider
'mole' is the definition.
(I've seen this before)
'inhabiting drains i'd eradicated' is the wordplay.
'inhabiting' indicates a hidden word.
'INSIDER' is hidden in the letters of 'drains id eradicated'.
(Other definitions for insider that I've seen before include "one who's in the know" , "Member of clique" , "One of us" , "one's not allowed to trade" , "Privileged member of a group" .)