Supported, nevertheless, with locks (10)
I believe the answer is:
buttressed
'supported' is the definition.
(similar in meaning)
'nevertheless with locks' is the wordplay.
'nevertheless' becomes 'but' (I've seen this in other clues).
'with locks' becomes 'tressed' (locks and tresses can both mean hair).
'but'+'tressed'='BUTTRESSED'
(Other definitions for buttressed that I've seen before include "Supported" , "Reinforced" , "held securely" .)