A little bit of what's served up in Palermo takeaway (4)
I believe the answer is:
atom
'a little bit' is the definition.
'what's served up in palermo takeaway' is the wordplay.
'what's served up' shows that the letters should be reversed in order.
'in' indicates a hidden word.
'mota' is hidden within 'palermo takeaway'.
'mota' in reverse letter order is 'ATOM'.
'of' acts as a link.
(Other definitions for atom that I've seen before include "Particle; molecule" , "A wee bit" , "Not much substance" , "Smallest component of an element" , "A mighty physical particle or bomb" .)