Hold back, delay (6)
I believe the answer is:
detain
This clue is a double definition.
'hold back' is the first definition.
(I've seen this in another clue)
'delay' is the second definition.
(I know that delay can be written as detain)
(Other definitions for detain that I've seen before include "Take into confinement" , "Keep back or arrest" , "Delay or take into custody" , "Hold in detention" , "Hold (someone) back" .)