Instrument's one featured in Sun (5)
I believe the answer is:
sitar
'instrument's' is the definition.
(sitar is a type of musical instrument)
'one featured in sun' is the wordplay.
'one' becomes 'i' (Roman numeral).
'featured in' indicates putting letters inside.
'sun' becomes 'star' (I've seen this in another clue).
'i' going within 'star' is 'SITAR'.
(Other definitions for sitar that I've seen before include "Large Indian lute" , "Lasting from morning to night" , "Plucked instrument" , "Indian string instrument" , "Hindu string instrument" .)