Model and artist turned up for instrument (5)
I believe the answer is:
sitar
'for instrument' is the definition.
(musical instrument)
'model and artist turned up' is the wordplay.
'model' becomes 'sit' (e.g. for a painting).
'and' is a charade indicator (letters next to each other).
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'turned up' says the letters should be written backwards.
'ra' back-to-front is 'ar'.
'sit'+'ar'='SITAR'
(Other definitions for sitar that I've seen before include "Long-necked musical instrument of India" , "Indian string instrument" , "Hindu stringed instrument" , "Astir with Indian long-necked lute" , "music-maker" .)