Work one worried could be addictive (6)
I believe the answer is:
opiate
'be addictive' is the definition.
I can't tell whether this defines the answer.
'work one worried' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'one' becomes 'i' (Roman numeral).
'worried' becomes 'ate' (something worrying may eat someone up).
'op'+'i'+'ate'='OPIATE'
'could' is the link.
Can you help me to learn more?
(Other definitions for opiate that I've seen before include "Narcotic drug" , "description of religion?" , "one soporific" , "Drug with an opium base" , "A sleep-inducing drug (6)" .)