Current that makes business turn (5,4)
I believe the answer is:
trade wind
'current' is the definition.
(I've seen this before)
'business turn' is the wordplay.
'business' becomes 'trade' (trade is a kind of business).
'turn' becomes 'wind' (I've seen this in another clue).
'trade'+'wind'='TRADE-WIND'
'that makes' is the link.
(Other definitions for trade wind that I've seen before include "shipowners once relied on" , "Steady breeze towards the equator" , "Current" , "Flow of air" .)