Delay or hold back (6)
I believe the answer is:
detain
I believe this clue is a double definition.
'delay' is the first definition.
(I know that delay is a is a more specific form of the action of delay)
'hold back' is the second definition.
(I've seen this in another clue)
(Other definitions for detain that I've seen before include "Hold (someone) back" , "Keep waiting or under restraint" , "Delay or take into custody" , "Hold back or keep under restraint" , "Sing to (someone)" .)