Drop off, however briefly (4)
I believe the answer is:
doze
'drop off' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for doze that I've seen before include "A short light sleep" , "Nod off" , "Take forty winks" , "Snooze" , "Go to sleep" .)