One might get bite in water tank, following one earlier (9)
I believe the answer is:
fisherman
'one might get bite in water' is the definition.
(someone who gets a bite from fish)
'tank following one earlier' is the wordplay.
'tank' becomes 'Sherman'.
'following' becomes 'f.' (used when citing page numbers etc).
'one' becomes 'i' (Roman numeral).
'earlier' is a charade indicator (letters next to each other).
'f'+'i'='fi'
'sherman' put after 'fi' is 'FISHERMAN'.
(Other definitions for fisherman that I've seen before include "He casts" , "Male angler" , "Male anger" , "One possibly catching sole" , "He's an angler" .)