Mendicant bear swallows horse (6)
I believe the answer is:
beggar
'mendicant' is the definition.
(synonyms)
'bear swallows horse' is the wordplay.
'swallows' means one lot of letters goes inside another.
'horse' becomes 'gg' (geegee or GG is a childish term for a horse).
'bear' going around 'gg' is 'BEGGAR'.
(Other definitions for beggar that I've seen before include "Solicitor" , "Reduce (someone) to poverty" , "poor chap" , "One lives by asking for money or food" , "Pauper who solicits" .)