First barrier’s best, somehow, to minimise one’s risk (5,4,4)
I believe the answer is:
hedge ones bets
'minimise one's risk' is the definition.
(hedging one's bets when gambling reduces risk)
'first barrier's best somehow' is the wordplay.
'first barrier's' becomes 'hedge one's' (the first hedge).
'somehow' is an anagram indicator.
'best' is an anagram of 'bets'.
'hedgeones'+'bets'='HEDGE ONES BETS'
'to' is the link.
(Other definitions for hedge ones bets that I've seen before include "Don't fully commit" , "Avoid committing oneself in a difficult situation" , "Guard against gambling losses" .)