Last pieces of Henry Moore and Barbara Hepworth? Sure! (4)
I believe the answer is:
yeah
'sure' is the definition.
(I've seen this in another clue)
'last pieces of henry moore and barbara hepworth?' is the wordplay.
'last pieces of' indicates one should take the final letters (I've seen 'last piece of' mean this).
'and' says to put letters next to each other.
'barbara hepworth?' becomes 'ah' (I can't explain this - if you can you should give a lot more credence to this answer).
The last letters of 'henry moore' are 'ye'.
'ye'+'ah'='YEAH'
Can you help me to learn more?
(Other definitions for yeah that I've seen before include "casual agreement" , "Casual form of yes" , "Informal agreement" , "Indeed" , "'She loves you, ..., ..., ...' (song)" .)