Told nine to work when slack (8)
I believe the answer is:
indolent
'slack' is the definition.
(thesaurus)
'told nine to work' is the wordplay.
'to work' is an anagram indicator (letters worked into a new order).
'told'+'nine'='toldnine'
'toldnine' anagrammed gives 'INDOLENT'.
'when' acts as a link.
(Other definitions for indolent that I've seen before include "Disinclined to exert oneself" , "Work-shy" , "Lazy, disinclined to work" , "Making no effort" , "not willing to work" .)