Grumble like a bloke who has nothing to eat (4)
I believe the answer is:
moan
'grumble' is the definition.
(I've seen this before)
'a bloke who has nothing to eat' is the wordplay.
'bloke who' becomes 'mn' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'has' indicates putting letters inside.
'nothing' becomes 'O' (looks like zero - 0).
'to eat' is an insertion indicator.
'mn' enclosing 'o' is 'mon'.
'a' placed inside 'mon' is 'MOAN'.
'like' acts as a link.
Can you help me to learn more?
(Other definitions for moan that I've seen before include "Expression of suffering" , "Beef" , "Lament; grumble" , "Complain, grumble" , "Low sound of pain" .)