Is it up to him to appear relatively unruffled? (3)
I believe the answer is:
dad
'is it up to him to appear relatively unruffled?' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'is it up to him' is the wordplay.
I cannot really understand how this works, but
'him' could be 'ad' and 'ad' is found within the answer.
A single letter 'd' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for dad that I've seen before include "Relation" , "Papa" , "Father, in short" , "Mum's mate" , "Pa" .)