Touched iron last, losing heart (4)
I believe the answer is:
felt
'touched' is the definition.
(feeling is a kind of touching)
'iron last losing heart' is the wordplay.
'iron' becomes 'Fe' (chemical symbol for iron).
'losing heart' suggests removing the centre.
'last' with its centre removed is 'lt'.
'fe'+'lt'='FELT'
(Other definitions for felt that I've seen before include "Material - perceived by touch" , "Sensed; fibre cloth" , "Touched the matted fabric" , "examined by touch" , "Handled - material" .)