Expression of relief after outsiders nurse male relative (6)
I believe the answer is:
nephew
'male relative' is the definition.
(I've seen this before)
'expression of relief after outsiders nurse' is the wordplay.
'expression of relief' becomes 'phew' (sound made when relieved).
'after' means one lot of letters go next to another.
'outsiders nurse' becomes 'ne' (I can't explain this - if you can you should give a lot more credence to this answer).
'phew' after 'ne' is 'NEPHEW'.
Can you help me to learn more?
(Other definitions for nephew that I've seen before include "Brother's/sister's son" , "Sister's son" , "Kinsman" , "Has a duty (to do something)" , "Male relative" .)