Gull-like bird — in water, normally (4)
I believe the answer is:
tern
'gull-like bird' is the definition.
(I've seen this before)
'in water normally' is the wordplay.
'in' indicates a hidden word.
'TERN' is hidden in the letters of 'water normally'.
(Other definitions for tern that I've seen before include "Rent out this gull" , "Seabird related to the gull" , "Winger" , "Gull-like seabird" , "Fork-tailed seabird" .)