Better to be rejected before tense agreement (4)
I believe the answer is:
pact
'agreement' is the definition.
(pact is a kind of agreement)
'better to be rejected before tense' is the wordplay.
'better' becomes 'cap' (I've seen this before**).
'to be rejected' says the letters should be written in reverse.
'before' means one lot of letters go next to another.
'tense' becomes 't' (abbreviation used in many dictionaries).
'cap' backwards is 'pac'.
'pac'+'t'='PACT'
(Other definitions for pact that I've seen before include "Agreement, bargain" , "Formal agreement between parties or states" , "Treaty, formal agreement" , "Alliance" , "Settlement" .)