Angler's fine with one tank (9)
I believe the answer is:
fisherman
'angler's' is the definition.
(I've seen this before)
'fine with one tank' is the wordplay.
'fine' becomes 'f' (abbreviation).
'with' is a charade indicator (letters next to each other).
'one' becomes 'i' (Roman numeral).
'tank' becomes 'Sherman'.
'f'+'i'+'sherman'='FISHERMAN'
(Other definitions for fisherman that I've seen before include "He's an angler" , "He casts" , "One possibly catching sole" , "St Peter" , "Male anger" .)