Contender initially campaigns with current partner (9)
I believe the answer is:
candidate
'contender' is the definition.
'initially campaigns with current partner' is the wordplay.
'initially' suggests taking the first letters.
'with' becomes 'and'.
'current' becomes 'i' (symbol for electric current).
'partner' becomes 'date'.
The initial letter of 'campaigns' is 'c'.
'c'+'and'+'i'+'date'='CANDIDATE'
(Other definitions for candidate that I've seen before include "who tries to get elected?" , "runner" , "Applicant, nominee 99)" , "Person who seeks appointment to an office" , "prospective employee?" .)