Drowsiest adult grabs forty winks (6)
I believe the answer is:
siesta
'forty winks' is the definition.
(siesta is a kind of forty winks)
'drowsiest adult grabs' is the wordplay.
'SIESTA' is hidden in amongst the letters.
However, I'm unsure how this is indicated.
Can you help me to learn more?
(Other definitions for siesta that I've seen before include "rest of the Spaniards" , "Afternoon relaxation" , "Rest of Spain" , "Seat is found for a Spanish rest period" , "A mid-day nap in Spain" .)