Cost of old-fashioned ballad (6)
I believe the answer is:
outlay
'cost' is the definition.
(I've seen this before)
'old-fashioned ballad' is the wordplay.
'old-fashioned' becomes 'out' (as opposed to 'in').
'ballad' becomes 'lay' ('lay' can be a synonym of 'ballad').
'out'+'lay'='OUTLAY'
'of' is the link.
(Other definitions for outlay that I've seen before include "Money expended" , "Money paid out" , "cost" , "Understood only by few" , "What it costs" .)