In winter, noticing seabird (4)
I believe the answer is:
tern
'seabird' is the definition.
(tern is a kind of seabird)
'in winter noticing' is the wordplay.
'in' indicates a hidden word.
'TERN' is hidden within 'winter noticing'.
(Other definitions for tern that I've seen before include "Winger" , "Seabird related to the gull" , "Small slender gull" , "Gull-like sea bird" , "Seabird, sounds like become sour" .)