It's a funny thing, what some birds do (4)
I believe the answer is:
hoot
'some birds do' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'it's a funny thing' is the wordplay.
I cannot quite understand how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is located in the answer.
The remaining letters 'hoo' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'what' acts as a link.
Can you help me to learn more?
(Other definitions for hoot that I've seen before include "Bird call; funny thing" , "Warning sound - something not given by the careless!" , "Screech" , "Shout of derision" , "Honk - laugh" .)