Veteran less good without a right hand (8)
I believe the answer is:
warhorse
'veteran' is the definition.
(I know that veteran can be written as warhorse)
'less good without a right hand' is the wordplay.
'less good' becomes 'worse' (I've seen this before).
'without' means one lot of letters goes inside another ('without' can be similar in meaning to 'outside').
'right hand' becomes 'RH' (abbreviation).
'a'+'rh'='arh'
'worse' enclosing 'arh' is 'WARHORSE'.
(Other definitions for warhorse that I've seen before include "steed?" , "Familiar piece of music" , "Belligerent" , "Old soldier" , "Copenhagen, say" .)