Keep going round for a light lunch? (4)
I believe the answer is:
roll
I believe this is a double definition.
'keep going round' is the first definition.
(as in rolling around)
'light lunch?' is the second definition.
(a roll might be eaten for lunch)
'for a' acts as a link.
(Other definitions for roll that I've seen before include "Barm cake" , "Bakery product" , "Bread - list - drumbeats" , "start recording film" , "Press" .)