Partner secures uncut supply just in time (8)
I believe the answer is:
punctual
'in time' is the definition.
(similar in meaning)
'partner secures uncut supply' is the wordplay.
'partner' becomes 'pal' (pal can mean a friend).
'secures' means one lot of letters goes inside another.
'supply' is an anagram indicator (in a supple way).
'uncut' anagrammed gives 'unctu'.
'pal' going around 'unctu' is 'PUNCTUAL'.
'just' acts as a link.
(Other definitions for punctual that I've seen before include "Exactly on time" , "Always on time for appointments" , "Arriving on time" , "Happening at the agreed time" , "Bang on time" .)