At the back there's a snow-bird (6)
I believe the answer is:
astern
'at the back' is the definition.
(I've seen this before)
'there's a snow-bird' is the wordplay.
'there's' says to put letters next to each other.
'snow' becomes 's' (this could be a standard abbreviation of which I'm unaware).
'bird' becomes 'tern' (tern is a kind of bird).
'a' next to 's' is 'as'.
'as'+'tern'='ASTERN'
Can you help me to learn more?
(Other definitions for astern that I've seen before include "Towards rear of a vessel" , "Rearward" , "Ran set (anag.)" , "Behind (a boat)" , "Toward the back of a boat" .)