Project was the endless fight (5)
I believe the answer is:
throw
'project' is the definition.
(I know that project can be written as throw)
'the endless fight' is the wordplay.
'endless' means to remove the last letter.
'fight' becomes 'row' (I've seen this in another clue).
'the' with its last letter removed is 'th'.
'th'+'row'='THROW'
'was' is the link.
(Other definitions for throw that I've seen before include "Toss" , "Fling; confound" , "puzzle" , "shot-put event?" , "Cast; give (party)" .)