Ring up, call (5)
I believe the answer is:
phone
This clue is a double definition.
'ring up' is the first definition.
(I've seen this in another clue)
'call' is the second definition.
(phone can mean to call by telephone)
(Other definitions for phone that I've seen before include "It converts sounds into signals and back again" , "Receiver" , "Call (someone)" , "Call, ring" , "Communications device" .)