Legislative body partly chosen at election (6)
I believe the answer is:
senate
'legislative body' is the definition.
(I've seen this before)
'partly chosen at election' is the wordplay.
'partly' indicates a hidden word.
'SENATE' can be found hidden inside 'chosen at election'.
(Other definitions for senate that I've seen before include "Roman state council" , "Political body" , "State assembly" , "House where politicians" , "The upper house in parliament or oireachtas" .)