Republicans in about the fifth month tie the knot again (7)
I believe the answer is:
remarry
'tie the knot again' is the definition.
(to tie the knot is to get married)
'republicans in about the fifth month' is the wordplay.
'republicans' becomes 'rr' (political abbreviation for republican repeated).
'in' is an insertion indicator.
'about' becomes 're' ('re' means regarding or about).
'the fifth month' becomes 'may' (I've seen this in another clue).
're'+'may'='remay'
'rr' inserted inside 'remay' is 'REMARRY'.
(Another definition for remarry that I've seen is " Wed again".)