In case of trouble, stopping PC is clearly right (13)
I believe the answer is:
incontestable
'clearly right' is the definition.
Both the definition and answer are adjectives. Perhaps you can see a link between them that I can't see?
'in case of trouble stopping pc' is the wordplay.
'case of' suggests removing the centre (like emptying a case).
'stopping' is an insertion indicator (stopping can mean blocking a gap).
'pc' becomes 'constable' (police constable).
'trouble' with its centre removed is 'te'.
'te' put within 'constable' is 'contestable'.
'in'+'contestable'='INCONTESTABLE'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for incontestable that I've seen before include "Without doubt" , "sure" , "Beyond dispute" .)