Demonstrate upturn in British rule with wise words (7)
I believe the answer is:
proverb
'wise words' is the definition.
(a wise saying)
'demonstrate upturn in british rule' is the wordplay.
'demonstrate' becomes 'prove' (synonyms).
'upturn in' says the letters should be written backwards.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'rule' becomes 'r' (legal abbreviation).
'b'+'r'='br'
'br' backwards is 'rb'.
'prove'+'rb'='PROVERB'
'with' is the link.
(Other definitions for proverb that I've seen before include "Wise saying" , "Generally true saying" , "Saying of great truth" , "Aphorism" , "Well-known statement incorporating general truth" .)