Heath has firstly to get car (5)
I believe the answer is:
motor
'car' is the definition.
(motor can informally mean a car)
'heath has firstly to' is the wordplay.
'heath' becomes 'moor' (both can mean a type of landscape).
'has' indicates putting letters inside.
'firstly' indicates taking the first letters.
The first letter of 'to' is 't'.
'moor' going around 't' is 'MOTOR'.
'get' is the link.
(Other definitions for motor that I've seen before include "go quickly" , "Make good progress" , "(Transport using) engine" , "Travel by car, engine" , "Move quickly" .)