Men taken in by Liberal Democrat peer (4)
I believe the answer is:
lord
'peer' is the definition.
(I've seen this before)
'men taken in by liberal democrat' is the wordplay.
'men' becomes 'or' (I've seen this in other clues).
'taken in by' means one lot of letters goes inside another.
'liberal democrat' becomes 'ld' (common abbreviation used in UK politics).
'or' placed within 'ld' is 'LORD'.
(Other definitions for lord that I've seen before include "Dismayed expression; ruler" , "Until 2006 the presiding officer of the House of Lords and head of the judiciary" , "Titled peer of the realm" , "Titled nobleman" , "Feudal superior" .)