Model in advert having no time (5)
I believe the answer is:
poser
'model' is the definition.
(synonyms)
'advert having no time' is the wordplay.
'advert' becomes 'poster' (I have seen 'Large advert ' mean 'poster' so perhaps 'advert' could also mean 'poster').
'having no' suggests deleting specific letters.
'time' becomes 't' (abbreviation).
'poster' with 't' removed is 'POSER'.
'in' acts as a link.
(Other definitions for poser that I've seen before include "Particularly baffling problem" , "Sticky problem" , "Ropes (anag.)" , "Tricky clue" , "Baffling question or problem" .)