British daredevil more vigorous (7)

I believe the answer is:
brisker
'more vigorous' is the definition.
Both the answer and definition are comparative adjectives. Perhaps they are linked in a way I don't understand?
'british daredevil' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'daredevil' becomes 'risker' (I've seen this in another clue).
'b'+'risker'='BRISKER'
Can you help me to learn more?
I've seen this clue in The Times.
Want a hint initially instead of a full solution?
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