Worker in quarantine (3)
I believe the answer is:
ant
'worker' is the definition.
(worker is a type of ant)
'in quarantine' is the wordplay.
'in' says the answer is hidden in the clue.
'ANT' is hidden within 'quarantine'.
(Other definitions for ant that I've seen before include "One more provident than Grasshopper" , "Social worker" , "Worker on the hill" , "Termite" , "Member of colony" .)