Engaged in campaigning, as bail is set (2,3,5)
I believe the answer is:
on the stump
'engaged in campaigning' is the definition.
(someone on the stump is politically campaigning)
'bail is set' is the wordplay.
I cannot really see how this works, but
an anagram of 'set' is 'est' which is located in the answer.
This explanation may well be incorrect...
'as' acts as a link.
(Other definitions for on the stump that I've seen before include "vote?" , "Bail imposed here" .)