Water bird; frogman (5)
I believe the answer is:
diver
I believe this clue is a double definition.
'water bird' is the first definition.
(I've seen this before)
'frogman' is the second definition.
(I know that frogman can be written as diver)
(Other definitions for diver that I've seen before include "One plunges head first into water" , "Frogman" , "Large waterbird" , "Water bird" , "Drive (anag.)" .)