Buy and sell (5)
I believe the answer is:
trade
I believe this is a double definition.
'buy' is the first definition.
(thesaurus)
'sell' is the second definition.
(trading is a kind of selling)
'and' acts as a link.
(Other definitions for trade that I've seen before include "Buying/selling of goods" , "Dealing in goods" , "Commercial exchange of goods and services" , "Calling" , "A skilled craft to earn living" .)