Root retired man associated with mother’s ruin (6)
I believe the answer is:
ginger
'root' is the definition.
(I know that ginger is a type of root vegetable)
'retired man associated with mother's ruin' is the wordplay.
'retired' shows that the letters should be reversed in order.
'man' becomes 'Reg' (short for Reginald).
'associated with' means one lot of letters go next to another.
'mother's ruin' becomes 'gin' (informal term for gin).
'reg' written backwards gives 'ger'.
'ger' put after 'gin' is 'GINGER'.
(Other definitions for ginger that I've seen before include "Spice - former Spice Girl" , "Spicy plant-stem" , "Fred Astaire's dancing partner" , "Fred Astaire's partner - Greer's gringo (anag)" , "Hot-tasting rootstock" .)