Penny finished with favourite doll (6)
I believe the answer is:
puppet
'doll' is the definition.
(I know that doll can be written as puppet)
'penny finished with favourite' is the wordplay.
'penny' becomes 'p' (short for pence).
'finished' becomes 'up' (eg 'time's up' means the time is finished).
'with' is a charade indicator (letters next to each other).
'favourite' becomes 'pet' (synonyms).
'p'+'up'+'pet'='PUPPET'
(Other definitions for puppet that I've seen before include "Pinocchio, e.g." , "One manipulated by another" , "It's worked with strings" , "Pawn - marionette" , "See 20" .)