Sell the last of the claret in the bar (6)
I believe the answer is:
retail
'sell' is the definition.
(I know that retail is a type of sell)
'last of the claret in the bar' is the wordplay.
'last of' indicates one should take the final letters.
'in' means one lot of letters goes inside another.
'the bar' becomes 'rail' (rail is a kind of bar).
The final letters of 'the claret' are 'et'.
'et' inserted inside 'rail' is 'RETAIL'.
'the' acts as a link.
(Other definitions for retail that I've seen before include "Sale of goods individually" , "I alter for trade that sells to public" , "Sell - supply account" , "Tell story" , "Sell - tell" .)