Men rattle about a bird (7)
I believe the answer is:
martlet
'a bird' is the definition.
Both the definition and answer are singular nouns.
Maybe they are linked in a way I don't understand?
'men rattle' is the wordplay.
I cannot really understand how this works, but
an anagram of 'rattle' is 'artlet' which is within the answer.
A single letter 'm' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'about' is the link.
Can you help me to learn more?
(Other definitions for martlet that I've seen before include "Heraldic swallow" , "Charge, being legless" , "Swallow (in heraldry)" , "Heraldic bird" , "... once swift" .)