Nearly the lot taking up weapons is really frightening (8)
I believe the answer is:
alarming
'really frightening' is the definition.
'alarming' can be an answer for 'frightening' (similar in meaning). I am unsure of the 'really' bit.
'nearly the lot taking up weapons' is the wordplay.
'nearly' means to remove the last letter.
'the lot' becomes 'all' (I've seen this in another clue).
'taking up weapons' becomes 'arming' (I've seen this before).
'all' with its last letter removed is 'al'.
'al'+'arming'='ALARMING'
'is' is the link.
Can you help me to learn more?
(Other definitions for alarming that I've seen before include "Disturbing, frightening" , "Scary, frightening" , "Frightening or warning of danger" , "causing fright" , "Striking with fear" .)