What MPs do in opposition (3)
I believe the answer is:
sit
'what mps do' is the definition.
The definition suggests a singular noun but the answer is not.
'in opposition' is the wordplay.
'in' says the answer is hidden in the clue.
'SIT' is hidden within 'opposition'.
Can you help me to learn more?
(Other definitions for sit that I've seen before include "as magistrates do" , "Brood" , "Take a pew, an exam" , "(Of bird) stay on nest" , "Take (an examination)" .)