Retaining custody (7)
I believe the answer is:
keeping
I believe this is a double definition.
'retaining' is the first definition.
('keep' can be a synonym of 'retain')
'custody' is the second definition.
(I've seen this before)
(Other definitions for keeping that I've seen before include "Not parting with" , "Custody" , "Charge" , "Holding on to" , "Delaying" .)