Through time, hard to stop gaunt monster (9)
I believe the answer is:
leviathan
'monster' is the definition.
(I know that leviathan is a type of monster)
'through time hard to stop gaunt' is the wordplay.
'through' becomes 'via' (via means going through).
'time hard' becomes 'th' (this could be a standard abbreviation of which I'm unaware).
'to stop' indicates putting letters inside (stopping can mean blocking a gap).
'gaunt' becomes 'lean' (similar in meaning).
'via'+'th'='viath'
'viath' inserted into 'lean' is 'LEVIATHAN'.
Can you help me to learn more?
(Other definitions for leviathan that I've seen before include "Monstrous beast" , "Huge (sea) monster" , "Autocratic monarch" , "Gigantic" , "An evil hat turns to anything of great size" .)