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' indicates the answer is hidden within the clue.
'ANT' is hidden in the letters of '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" .)