Rents going up, it’s not so much weak (10)
I believe the answer is:
spiritless
'weak' is the definition.
Both the definition and answer are adjectives. Perhaps there's a link between them I don't understand?
'rents going up it's not so much' is the wordplay.
'rents' becomes 'rips' ('rip' can be a synonym of 'rent').
'going up' says the letters should be written backwards.
'not so much' becomes 'less' (I've seen this in other clues).
'rips' back-to-front is 'spir'.
'spir'+'it'+'less'='SPIRITLESS'
Can you help me to learn more?
(Another definition for spiritless that I've seen is " Lacking ardour".)