Research into model vehicles (5)
I believe the answer is:
delve
'research' is the definition.
(I've seen this before)
'into model vehicles' is the wordplay.
'into' indicates the answer is hidden within the clue.
'DELVE' can be found hidden inside 'model vehicles'.
(Other definitions for delve that I've seen before include "probe deeply" , "Dig - investigate" , "Dig up - search" , "Hollow" , "Look closely (into)" .)