Put back model in collection (4)
I believe the answer is:
stet
'put back' is the definition.
(I've seen this in other clues)
'model in collection' is the wordplay.
'model' becomes 't' (Ford Model T car).
'in' indicates putting letters inside.
'collection' becomes 'set' (set is a kind of collection).
't' put within 'set' is 'STET'.
(Other definitions for stet that I've seen before include "Ignore crossing" , "Let it stand (editing mark)" , "Let it stand (L)" , "Let it stand (on proofs)" , "Let it stand (on proof)" .)