Grounds for an about turn, just in case (5)
I believe the answer is:
cause
I believe this clue is a quadruple definition!!
'grounds' is the first definition.
(I've seen this before)
'for' is the second definition.
(thesaurus)
'an about turn' is the third definition.
The definition and answer can be both acts as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'just in case' is the fourth definition.
'cause' can be an answer for 'case' (thesaurus). I'm not certain of the 'just in' bit.
Can you help me to learn more?
(Other definitions for cause that I've seen before include "A movement or charity- usually good" , "Grounds" , "Produce (an effect)" , "Genesis" , "Give rise to" .)