The last word about the Italian teacher’s first complaint (7)
I believe the answer is:
ailment
'complaint' is the definition.
(synonyms)
'the last word about the italian teacher's first' is the wordplay.
'the last word' becomes 'amen' (last word in a prayer).
'about' indicates putting letters inside.
'the italian' becomes 'il' ('the' in Italian).
'teacher's first' becomes 't' (1st letter of 'teacher').
'amen' placed around 'il' is 'ailmen'.
'ailmen'+'t'='AILMENT'
(Other definitions for ailment that I've seen before include "Physical disorder" , "Tim Alen has an odd indisposition." , "Malady" , "Tummy upset, for instance" , "problem" .)