Party I held in bloke's field (6)
I believe the answer is:
domain
'field' is the definition.
(I know that field can be written as domain)
'party i held in bloke's' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'held in' indicates putting letters inside.
'bloke' becomes 'man' (informal term for a man).
'i' going inside 'man' is 'main'.
'do'+'main'='DOMAIN'
(Other definitions for domain that I've seen before include "Field of thought or activity" , "Kingdom or realm" , "Sphere or territory" , "Realm or range of influence" , "Range of influence or field of activity" .)