In that, again, it is intimidating (6)
I believe the answer is:
threat
'it is intimidating' is the definition.
The definition suggests a singular noun which matches the answer.
'in that again' is the wordplay.
'in' indicates putting letters inside.
'again' becomes 're'.
'that' going around 're' is 'THREAT'.
Can you help me to learn more?
(Other definitions for threat that I've seen before include "An intimidatory warning" , "Hatter (anag)" , "Potential source of danger" , "Indication of danger" , "Menacing words" .)