It's charged by leaders of imperial cavalry and foot (5)
I believe the answer is:
ionic
'foot' is the definition.
(thesaurus)
'it's charged by leaders of imperial cavalry' is the wordplay.
'it's charged' becomes 'ion' (I've seen this in other clues).
'by' says to put letters next to each other.
'leaders of' says to take the initial letters.
The initial letters of 'imperial cavalry' is 'ic'.
'ion'+'ic'='IONIC'
'and' is the link.
(Other definitions for ionic that I've seen before include "A type of classical Greek column" , "Classic order of architecture" , "Classical dialect" , "Classic form of dialect" , "Like a sort of bond" .)