Capital chap supporting upset mother (5)
I believe the answer is:
amman
'capital' is the definition.
(capital of Jordan)
'chap supporting upset mother' is the wordplay.
'chap' becomes 'man' (chap can mean a man).
'supporting' means one lot of letters go next to another (in a down clue, some letters go below others).
'upset' shows that the letters should be reversed in order.
'mother' becomes 'ma' (Ma is another word for mother or mum).
'ma' reversed gives 'am'.
'man' put after 'am' is 'AMMAN'.
(Other definitions for amman that I've seen before include "Jordan's capital" , "A capital f-fellow in Jordan?" , "Jordanian capital" , "Jordanian city" , "City of Jordan" .)