In favour of supporting patient (10)
I believe the answer is:
forbearing
'patient' is the definition.
(similar in meaning)
'in favour of supporting' is the wordplay.
'in favour of' becomes 'for' (being for a particular cause).
'supporting' becomes 'bearing' (similar in meaning).
'for'+'bearing'='FORBEARING'
(Other definitions for forbearing that I've seen before include "Patient, restrained" , "Understanding" .)