A supporter legally without a friend (3)
I believe the answer is:
leg
'a supporter' is the definition.
(eg support for a table)
'legally without a friend' is the wordplay.
'without' suggests deleting specific letters.
'a friend' becomes 'ally' (an ally is a friend or supporter).
'legally' with 'ally' taken out is 'LEG'.
(Other definitions for leg that I've seen before include "Poultry portion" , "Limb; stage" , "prop" , "part of course" , "Gigot" .)