Notice ring on tailless bird (7)
I believe the answer is:
discern
'notice' is the definition.
(I've seen this before)
'ring on tailless bird' is the wordplay.
'ring' becomes 'disc' (both are round objects).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'tailless bird' becomes 'ern' (ern is a kind of bird. I am not sure about the 'tailless' bit.).
'disc'+'ern'='DISCERN'
Can you help me to learn more?
(Other definitions for discern that I've seen before include "Recognise, find out" , "Pick out" , "See" , "Cinders (anag)" , "Make out, distinguish by eye" .)