A saint will protect biblical leader in onslaught (7)
I believe the answer is:
assault
'in onslaught' is the definition.
(I know that assault is part of attack)
'a saint will protect biblical leader' is the wordplay.
'saint' becomes 'st' (abbreviation).
'will protect' means one lot of letters goes inside another (inserted letters are held or protected).
'biblical leader' becomes 'saul' (I am not sure about this - if you are sure you should believe this answer much more).
'st' placed around 'saul' is 'ssault'.
'a'+'ssault'='ASSAULT'
Can you help me to learn more?
(Other definitions for assault that I've seen before include "Attack violently" , "Mount an attack" , "Violent attack in action or words" , "Attack physically" , "Lash" .)