Bring on a turn, just in case (5)
I believe the answer is:
cause
'bring' is the definition.
(thesaurus)
'turn just in case' is the wordplay.
'turn just' becomes 'u' (a 'U-turn' is a kind of turn. I am not sure about the 'just' bit.).
'in' indicates putting letters inside.
'u' put inside 'case' is 'CAUSE'.
'on a' is the link.
Can you help me to learn more?
(Other definitions for cause that I've seen before include "why some people fight" , "Produce (an effect)" , "Grounds" , "Give rise to" , "Make happen; something deserving support" .)