Independent parliamentarian to back hospital department without effect (8)
I believe the answer is:
impotent
'without effect' is the definition.
(impotent can mean powerless or ineffectual)
'independent parliamentarian to back hospital department' is the wordplay.
'independent' becomes 'i'.
'parliamentarian' becomes 'MP'.
'back' shows that the letters should be reversed in order.
'hospital department' becomes 'ENT' (abbreviation for Ear, Nose and Throat department).
'to' written backwards gives 'ot'.
'i'+'mp'+'ot'+'ent'='IMPOTENT'
(Other definitions for impotent that I've seen before include "Mon petit may be powerless" , "Powerless like mon petit" , "Helpless, powerless" , "Ineffective" , "Lacking power" .)