Chariot out of control, source of claim regarding foot (8)
I believe the answer is:
trochaic
'regarding foot' is the definition.
(I know this)
'chariot out of control source of claim' is the wordplay.
'out of control' indicates an anagram.
'source of' says to take the initial letters (the start - or source - of the word).
The first letter of 'claim' is 'c'.
'chariot' is an anagram of 'trochai'.
'trochai'+'c'='TROCHAIC'
(Other definitions for trochaic that I've seen before include "Like some verse forms" , "with feet" .)