Weak parliament holds president back (5)
I believe the answer is:
tepid
'weak' is the definition.
(thesaurus)
'parliament holds president back' is the wordplay.
'parliament' becomes 'diet' (I've seen this before).
'holds' is an insertion indicator.
'president' becomes 'p' (common abbreviation eg in VP).
'back' is a reversal indicator.
'diet' going around 'p' is 'dipet'.
'dipet' in reverse letter order is 'TEPID'.
(Other definitions for tepid that I've seen before include "Unenthusiastic - cool" , "Moderately warm" , "Not very warm (water)" , "Luke warm" , "Half-hearted" .)