Music-maker’s old vehicle, trendy one (7)
I believe the answer is:
ocarina
'music-maker's' is the definition.
(type of musical instrument)
'old vehicle trendy one' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'vehicle' becomes 'car' (car is a kind of vehicle).
'trendy' becomes 'in' ('in' can mean fashionable).
'one' becomes 'a' (a thing is one thing).
'o'+'car'+'in'+'a'='OCARINA'
(Other definitions for ocarina that I've seen before include "Small egg-shaped wind instrument with holes for the fingers" , "dated instrument" , "Bird-shaped flute" , "Play a musical toy in the ICA, Nora" , "Inca oar made into a musical instrument" .)