Surprising dim person I kept behind bars (10)
I believe the answer is:
imprisoned
'behind bars' is the definition.
(I've seen this before)
'surprising dim person i' is the wordplay.
'surprising' is an anagram indicator.
'dim'+'person'+'i'='dimpersoni'
'dimpersoni' with letters rearranged gives 'IMPRISONED'.
'kept' is the link.
(Other definitions for imprisoned that I've seen before include "Locked up" , "Put away" , "in jail" , "behind bars" .)