Subtract end of the journey but this its first three (5)
I believe the answer is:
minus
'three' is the definition.
Both the definition and answer are adjectives. Perhaps there's an association between them I don't understand?
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for minus that I've seen before include "Lacking; negative" , "'Take away' sign" , "(Of temperature) below zero" , "Negative sign - negative thing" , "Less, without" .)