Loud crone holding gentleman back (6)
I believe the answer is:
garish
'loud' is the definition.
(synonyms)
'crone holding gentleman back' is the wordplay.
'crone' becomes 'hag' (synonyms).
'holding' is an insertion indicator.
'gentleman' becomes 'sir' (I've seen this before).
'back' is a reversal indicator.
'hag' placed around 'sir' is 'hsirag'.
'hsirag' reversed gives 'GARISH'.
(Other definitions for garish that I've seen before include "Overbright and showy" , "Gaudy, excessively bright" , "Gaudy, lurid" , "Colourful in a vulgar manner" , "Gaudy, showy" .)