Specious excuse from platoon leader regarding message (7)
I believe the answer is:
pretext
'specious excuse' is the definition.
(I've seen this before)
'platoon leader regarding message' is the wordplay.
'leader' suggests taking the first letters.
'regarding' becomes 're'.
'message' becomes 'text' (I've seen this before**).
The first letter of 'platoon' is 'p'.
'p'+'re'+'text'='PRETEXT'
'from' is the link.
(Other definitions for pretext that I've seen before include "Stalking-horse" , "Alleged reason" , "Excuse, ruse" , "Ostensible reason" , "False reason as justification for an action" .)