London hospital making good northern grub (4)
I believe the answer is:
nosh
'grub' is the definition.
(I've seen this before)
'london hospital making good northern' is the wordplay.
I cannot quite understand how this works, but
'hospital' could be 'h' (abbreviation for hospital on maps) and 'h' is found within the answer.
'northern' could be 'n' (abbreviation e.g. N. Ireland) and 'n' is present in the answer.
The remaining letters 'os' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for nosh that I've seen before include "'Food, grub (4)'" , "Scoff" , "Food (Yiddish)" , "cuisine" , "(Eat) a snack" .)