9 across
I
will
block
rejection
of
unconvincing
message
(5)
I will block rejection of unconvincing message (5)
hints
0
checks
0
hints
The definition is at the end of the clue.
How the clue works
message is your definition here. Take unconvincing — that's LAME — flip it to get EMAL, then slot I ("I will" giving us "I") inside to land on E-M-A-I-L.