One in hot car unexpectedly finding bean (7)
I believe the answer is:
haricot
'bean' is the definition.
(haricot is a type of bean)
'one in hot car unexpectedly' is the wordplay.
'one' becomes 'i' (Roman numeral).
'in' is an insertion indicator.
'unexpectedly' indicates anagramming the letters.
'hot'+'car'='hotcar'
'hotcar' is an anagram of 'harcot'.
'i' going inside 'harcot' is 'HARICOT'.
'finding' acts as a link.
(Other definitions for haricot that I've seen before include "Vegetable" , "Variety of bean" , "kind of ragout" , "Type of bean in a chariot" , "French bean" .)