The first to sew? Not us (4)
I believe the answer is:
them
'not us' is the definition.
(I've seen this before)
'the first to sew?' is the wordplay.
'the first to' becomes 't' (hst letter of 'to').
'sew?' becomes 'hem' (I can't explain this - if you can you should give a lot more credence to this answer).
't'+'hem'='THEM'
Can you help me to learn more?
(Other definitions for them that I've seen before include "(To/from) those people" , "Others" , "Let -- eat cake" , "... in another case, they" , "Perhaps, the Opposition" .)