Bird in icy north (7)
I believe the answer is:
bittern
'bird in icy north' is the definition.
'bittern' can be an answer for 'bird' (I've seen this before). I'm unsure of the 'in icy north' bit.
'bird in' is the wordplay.
I cannot quite see how this works, but
'bird' could be 'tern' (tern is a kind of bird) and 'tern' is present in the answer.
The remaining letters 'bit' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
(Other definitions for bittern that I've seen before include "found hidden in reed-beds" , "Marsh bird of the heron family" , "Bird that booms" , "Bird of marshes" , "Booming marsh bird" .)