Guess I am stuck in car? (8)
I believe the answer is:
estimate
'guess' is the definition.
(I know that guess can be written as estimate)
'i am stuck in car?' is the wordplay.
'i am' becomes 'I'm' (contraction).
'stuck in' is an insertion indicator.
'car?' becomes 'estate' (type of car).
'im' put inside 'estate' is 'ESTIMATE'.
(Other definitions for estimate that I've seen before include "Tease Tim (anag.)" , "Form opinion of - tea times (anag)" , "Calculate in approximate way" , "Statement of expected cost" , "calculate aproximately" .)