Car running hot in bend (4)
I believe the answer is:
arch
'bend' is the definition.
(arching is a kind of bending)
'car running hot' is the wordplay.
'running' indicates an anagram.
'hot' becomes 'h' (abbreviation eg on taps).
'car' is an anagram of 'arc'.
'arc'+'h'='ARCH'
'in' acts as a link.
(Other definitions for arch that I've seen before include "Knowing, sly" , "Curved spanning structure" , "Structural curve" , "Curved vault" , "Curved entrance" .)