Bag and keep everybody in detention (7)
I believe the answer is:
holdall
'bag' is the definition.
(I know that holdall is a type of bag)
'keep everybody in detention' is the wordplay.
I cannot really see how this works, but
'keep' could be 'hold' (both can mean to have or possess something) and 'hold' is found within the answer.
'everybody' could be 'all' (all people) and 'all' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'and' acts as a link.
Can you help me to learn more?
(Other definitions for holdall that I've seen before include "Bag (contents unlimited?)" , "Large strong bag with handles or shoulder strap" , "Large carrying bag" , "Item of luggage" , "retainer" .)