Identify loose seat in car (9)
I believe the answer is:
ascertain
'identify' is the definition.
(ascertain can mean to calculate or identify)
'loose seat in car' is the wordplay.
'loose' indicates an anagram (letters are loosened from their original positions).
'seat'+'in'+'car'='seatincar'
'seatincar' anagrammed gives 'ASCERTAIN'.
(Other definitions for ascertain that I've seen before include "Learn" , "Discover" , "settle" , "Become aware" , "Verify" .)