Mad as called into action (8)
I believe the answer is:
deranged
'mad' is the definition.
(I've seen this in another clue)
'called into action' is the wordplay.
'called' becomes 'rang' (called on the phone).
'into' indicates putting letters inside.
'action' becomes 'deed' (deed is a kind of action).
'rang' going within 'deed' is 'DERANGED'.
'as' is the link.
(Other definitions for deranged that I've seen before include "irrational" , "Mentally unbalanced" , "Lunatic" , "Upset" , "Gardened, being quite mad" .)