Former champion to consider touring British compound (10)
I believe the answer is:
exacerbate
'compound' is the definition.
(I've seen this in another clue)
'former champion to consider touring british' is the wordplay.
'former' becomes 'ex' (prefix meaning former or onetime).
'champion' becomes 'ace' (both can mean a person excelling at something).
'to consider' becomes 'rate' (I've seen this in another clue).
'touring' means one lot of letters goes inside another (touring can mean going round).
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'rate' going around 'b' is 'rbate'.
'ex'+'ace'+'rbate'='EXACERBATE'
(Other definitions for exacerbate that I've seen before include "Make (a bad thing) worse" , "Worsen" , "Provoke" .)