Religious ascetic just about heading for Kabul (5)
I believe the answer is:
fakir
'religious ascetic' is the definition.
(I've seen this before)
'just about heading for kabul' is the wordplay.
'just' becomes 'fair' (just can mean fair in the sense of showing justice).
'about' means one lot of letters goes inside another.
'heading for' suggests taking the first letters.
The initial letter of 'kabul' is 'k'.
'fair' going around 'k' is 'FAKIR'.
(Other definitions for fakir that I've seen before include "Indian religious ascetic" , "Ascetic in India" , "Eastern holy man" , "Holy man of the East" , "Religious mendicant in India" .)