Plea to have dinner in lobby (8)
I believe the answer is:
entreaty
'plea' is the definition.
(I've seen this before)
'have dinner in lobby' is the wordplay.
'have dinner' becomes 'eat' (I've seen this in another clue).
'in' indicates putting letters inside.
'lobby' becomes 'entry' (I've seen this before).
'eat' put inside 'entry' is 'ENTREATY'.
'to' acts as a link.
(Other definitions for entreaty that I've seen before include "Appeal" , "Supplication" , "petition" , "An earnest or emotional request" , "Teeny rat (anag.)" .)