Hide the left and right in Britain (4)
I believe the answer is:
lurk
'hide' is the definition.
(I know that lurk is a more specific form of hide)
'left and right in britain' is the wordplay.
'left' becomes 'l' (common abbreviation).
'and' means one lot of letters go next to another.
'right' becomes 'r' (common abbreviation).
'in' is an insertion indicator.
'britain' becomes 'uk' (synonyms).
'r' placed inside 'uk' is 'urk'.
'l'+'urk'='LURK'
'the' acts as a link.
(Other definitions for lurk that I've seen before include "Skulk, hide" , "Hang around furtively" , "Lie hidden" , "View an online forum without contributing" , "Hide menacingly" .)