The gentleman got up only to have something to eat (7)
I believe the answer is:
rissole
'something to eat' is the definition.
(rissole is a kind of food)
'the gentleman got up only' is the wordplay.
'the gentleman' becomes 'sir' (I've seen this before).
'got up' shows that the letters should be reversed in order.
'only' becomes 'sole' (synonyms).
'sir' reversed gives 'ris'.
'ris'+'sole'='RISSOLE'
'to have' is the link.
(Other definitions for rissole that I've seen before include "Compressed meat and spices in breadcrumbs, fried" , "Fried meat/breadcrumb ball" , "Minced meat or fish deep fried in egg and breadcrumbs" , "Lorises (anag)" , "Fried ball of minced food" .)