Some expressing a sigh of relief (1,3)
I believe the answer is:
a few
'some' is the definition.
(I've seen this before)
'a sigh of relief' is the wordplay.
I cannot really understand how this works, but
'a' is found in the answer.
The remaining letters 'few' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'expressing' is the link.
Can you help me to learn more?
(Other definitions for a few that I've seen before include "Sundry" , "Certainly not many" .)