Regular payment heading for worker on time (4)
I believe the answer is:
wage
'regular payment' is the definition.
(wage is a kind of regular payment)
'heading for worker on time' is the wordplay.
'heading for' suggests taking the first letters.
'on' means one lot of letters go next to another.
'time' becomes 'age' (an age is a period of time).
The initial letter of 'worker' is 'w'.
'w'+'age'='WAGE'
(Other definitions for wage that I've seen before include "Carry on - remuneration" , "practise" , "Earnings - carry on" , "Money paid to worker" , "Pursue" .)