Reveal support for discharge, although it's faint (4,3)
I believe the answer is:
pass out
'it's faint' is the definition.
(synonyms)
'reveal support for discharge' is the wordplay.
'reveal' becomes 'out' (outing is a kind of revealing).
'support for' means one lot of letters go next to another (in a down clue, some letters 'support' others).
'discharge' becomes 'pass' (passing is a kind of discharging).
'out' after 'pass' is 'PASS-OUT'.
'although' acts as a link.
(Other definitions for pass out that I've seen before include "Lose consciousness" , "Faint - finish military training" , "Become unconscious" , "Faint - or complete military training" , "In the army, do so having proved ready" .)