Bumpkin agreed to occupy pastureland after reflection (5)
I believe the answer is:
yokel
'bumpkin' is the definition.
(synonyms)
'agreed to occupy pastureland after reflection' is the wordplay.
'agreed' becomes 'ok' (eg when responding to an offer).
'to occupy' is an insertion indicator (inserted letters occupy or enter the word).
'pastureland' becomes 'ley' (synonyms).
'after reflection' says the letters should be written in reverse.
'ley' back-to-front is 'yel'.
'ok' going within 'yel' is 'YOKEL'.
(Other definitions for yokel that I've seen before include "Rustic - peasant" , "Simple rustic" , "Hayseed" , "Bumpkin - rustic" , "Hick" .)