Worry about electoral system for thirty days (5)
I believe the answer is:
april
'thirty days' is the definition.
(I've seen this before)
'worry about electoral system' is the wordplay.
'worry' becomes 'ail' (I've seen this in another clue).
'about' is an insertion indicator.
'electoral system' becomes 'pr' (I've seen this in other clues).
'ail' going around 'pr' is 'APRIL'.
'for' is the link.
(Other definitions for april that I've seen before include "First month of the year with 30 days" , "4th month" , "''... is the cruellest month'' (TS Eliot)" , "Spring month" , "Springtime rain" .)