Mostly wheezy Southern seabirds (7)
I believe the answer is:
puffins
'seabirds' is the definition.
(I know this)
'mostly wheezy southern' is the wordplay.
I cannot really understand how this works, but
'southern' could be 's' (abbreviation) and 's' is present in the answer.
The remaining letters 'puffin' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for puffins that I've seen before include "Black and white diving birds" , "Seabirds with brightly-coloured bills" , "Bright-billed auks" .)