Cut demand to keep variable stock (9)
I believe the answer is:
hackneyed
'stock' is the definition.
(both can mean cliche)
'cut demand to keep variable' is the wordplay.
'cut' becomes 'hack' (hacking is a kind of cutting).
'demand' becomes 'need' (synonyms).
'to keep' means one lot of letters goes inside another.
'variable' becomes 'y' (algebra).
'need' placed around 'y' is 'neyed'.
'hack'+'neyed'='HACKNEYED'
(Other definitions for hackneyed that I've seen before include "pedestrian" , "Stereotyped" , "using familiar phraseology?" , "Overworked" , "Trite, stale" .)