Having come down, it's on the left (3)
I believe the answer is:
lit
'left' is the definition.
Both the definition and answer are adjectives. Maybe they are linked in a way I don't understand?
'having come down it's on' is the wordplay.
I cannot really see how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is present in the answer.
The remaining letters 'li' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'the' is the link.
Can you help me to learn more?
(Other definitions for lit that I've seen before include "Settled" , "fine writing in condensed form" , "Set afire" , "Burning" , "Creative writing, in short" .)