Square loaf mostly devoured by old man (5)
I believe the answer is:
plaza
'square' is the definition.
(synonyms)
'loaf mostly devoured by old man' is the wordplay.
'loaf' becomes 'laze' (as in to loaf or laze around idly).
'mostly' means to remove the last letter.
'devoured by' indicates putting letters inside.
'old man' becomes 'pa' (both can mean father).
'laze' with its last letter taken off is 'laz'.
'laz' put inside 'pa' is 'PLAZA'.
(Other definitions for plaza that I've seen before include "Open urban square or public area" , "Public square for pedestrians" , "Hotel" , "Public square, in Italy" , "Public square, as in Spanish town" .)