Surprised, began to ring the number (8)
I believe the answer is:
startled
'surprised' is the definition.
('startled' can be similar in meaning to 'surprised')
'began to ring the number' is the wordplay.
'began' becomes 'started' ('start' can be a synonym of 'begin').
'to ring' is an insertion indicator.
'the number' becomes 'l' (L is an example**).
'started' placed around 'l' is 'STARTLED'.
(Other definitions for startled that I've seen before include "Frightened or surprised suddenly" , "Frightened or suprised suddenly" , "Caused sudden alarm" , "Affrighted" , "Taken aback" .)