Threshold for measure in support of disheartened benefactor (8)
I believe the answer is:
doorstep
'threshold' is the definition.
('doorstep' can be a synonym of 'threshold')
'measure in support of disheartened benefactor' is the wordplay.
'measure' becomes 'step' (step is a kind of measure**).
'in support of' means one lot of letters go next to another (I've seen this in other clues).
'disheartened' suggests removing the centre.
'benefactor' becomes 'donor' (donor is a kind of benefactor).
'donor' with its middle taken out is 'door'.
'step' put after 'door' is 'DOORSTEP'.
'for' is the link.
(Other definitions for doorstep that I've seen before include "go canvassing" , "Torpedos (anag.)" , "Old song: ` `Oh Mother Kelly's ........' '" , "Threshold stair" , "slab at threshold" .)