Established area covered by US phone briefly: it may give you a tinkle (7)

I believe the answer is:
celesta
'us phone briefly it may give you a tinkle' is the definition.
I can't tell whether this definition defines the answer.
'established area covered by' is the wordplay.
'established' becomes 'est' (abbreviation).
'area' becomes 'a' (maths abbreviation).
'covered' becomes 'cel' (I am not sure about this - if you are sure you should believe this answer much more).
'by' says to put letters next to each other.
'est'+'a'='esta'
'esta' put after 'cel' is 'CELESTA'.
Can you help me to learn more?
(Other definitions for celesta that I've seen before include "a bunch of keys?" , "Play this" , "one giving out notes" , "Keyboard percussion instrument giving a bell-like sound" , "Musical instrument" .)
