Attendant on the right uses radio device (5)
I believe the answer is:
pager
'radio device' is the definition.
'pager' can be an answer for 'device' (I have seen 'Bleeping device' mean 'pager' so perhaps 'device' could also mean 'pager'). I'm unsure of the 'radio' bit.
'attendant on the right' is the wordplay.
'attendant' becomes 'page' (page is a kind of attendant).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'the right' becomes 'r' (common abbreviation).
'page'+'r'='PAGER'
'uses' is the link.
Can you help me to learn more?
(Other definitions for pager that I've seen before include "Contact device" , "Electronic messaging device" , "Way to contact" , "This may summon one" , "Old electronic bleeping device" .)