One about to follow a court battle (6)
I believe the answer is:
action
'battle' is the definition.
(military action)
'one about to follow a court' is the wordplay.
'one' becomes 'i' (Roman numeral).
'about' becomes 'on' (**).
'to follow' says to put letters next to each other.
'court' becomes 'ct'.
'i'+'on'='ion'
'a'+'ct'='act'
'ion' put after 'act' is 'ACTION'.
(Other definitions for action that I've seen before include "Director's cue?" , "Operation - lawsuit" , "instruction from director" , "Fighting - lawsuit" , "Watch operating mechanism" .)