Desperately need tot in custody (9)
I believe the answer is:
detention
'custody' is the definition.
(I know that custody can be written as detention)
'desperately need tot in' is the wordplay.
'desperately' indicates an anagram.
'need'+'tot'+'in'='needtotin'
'needtotin' anagrammed gives 'DETENTION'.
(Other definitions for detention that I've seen before include "Confinement" , "Arrest; school punishment" , "After-school punishment" , "Custody" .)