Unite firm New Jersey supports with other industrial name initially (7)
I believe the answer is:
conjoin
'unite' is the definition.
(I know that conjoin is a more specific form of the action the unite)
'firm new jersey supports with other industrial name initially' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'new jersey' becomes 'nj' (abbreviation).
'supports' says to put letters next to each other (in a down clue, bottom letters 'support' others).
'with' is a charade indicator (letters next to each other).
'initially' indicates taking the first letters.
The first letters of 'other industrial name' is 'oin'.
'co'+'nj'+'oin'='CONJOIN'
(Other definitions for conjoin that I've seen before include "put together" , "Team up with" .)