Pager — sound of alarm’s piercing; one’s used to working with buzzers (9)
I believe the answer is:
beekeeper
'one's used to working with buzzers' is the definition.
I can't judge whether this defines the answer.
'pager sound of alarm's piercing' is the wordplay.
'pager' becomes 'beeper' (I've seen this before).
'sound of alarm' becomes 'eek' (I've seen this before).
'piercing' is an insertion indicator (some letters pierce a hole in others).
'beeper' placed around 'eek' is 'BEEKEEPER'.
Can you help me to learn more?
(Other definitions for beekeeper that I've seen before include "Hive tender" , "Honey farmer" , "Person in charge of apiary" , "Apiarist" , "There may be a buzz about him" .)