Excuse used before the advent of phone messaging (7)
I believe the answer is:
pretext
I believe this clue is a double definition.
'excuse' is the first definition.
(I've seen this in another clue)
'before the advent of phone messaging' is the second definition.
(pre text messaging)
'used' is the link.
(Other definitions for pretext that I've seen before include "Ostensible reason" , "Stalking-horse" , "False reason as justification for an action" , "Excuse, ruse" , "Fictitious excuse" .)