Rate change involving ten more (5)
I believe the answer is:
extra
'more' is the definition.
(I've seen this before)
'rate change involving ten' is the wordplay.
'change' indicates an anagram.
'involving' is an insertion indicator.
'ten' becomes 'X' (Roman numeral).
'rate' anagrammed gives 'etra'.
'etra' enclosing 'x' is 'EXTRA'.
(Other definitions for extra that I've seen before include "No-ball or wide, perhaps?" , "comes to 16 [TEST MATCH]" , "There's more" , "entry on scorecard?" , "Score not made by 34 [CRICKETER]" .)