Line in meals, perhaps, offering excessive supply (5)
I believe the answer is:
flood
'excessive supply' is the definition.
'line in meals perhaps' is the wordplay.
'line' becomes 'l'.
'in' means one lot of letters goes inside another.
'meals perhaps' becomes 'food'.
'l' placed into 'food' is 'FLOOD'.
'offering' acts as a link.
(Other definitions for flood that I've seen before include "Inundation" , "Brim over" , "Deluge" , "Inundate" , "Overflow of water" .)