Coat the lady will take on account (7)
I believe the answer is:
shellac
'coat' is the definition.
(I've seen this before)
'the lady will take on account' is the wordplay.
'the lady will' becomes 'shell'.
'take on' says to put letters next to each other.
'account' becomes 'ac'.
'shell'+'ac'='SHELLAC'
(Other definitions for shellac that I've seen before include "Sort of resin" , "Take a shine to" , "Resin for varnishing" , "Resin in flakes, used to making varnish" , "old record" .)