Becoming a supporter with some hesitation (6)
I believe the answer is:
proper
'becoming' is the definition.
(similar in meaning)
'a supporter with some hesitation' is the wordplay.
'a supporter' becomes 'prop' (I've seen this before).
'with' says to put letters next to each other.
'some hesitation' becomes 'er' (sound made while hesitating - um, er).
'prop'+'er'='PROPER'
(Other definitions for proper that I've seen before include "Befitting" , "Authentic" , "Correct in behaviour" , "Correct; respectable" , "Actual" .)