Gun resembles a gold cat with a twitch (9)
I believe the answer is:
automatic
'gun' is the definition.
(I know that automatic is a type of pistol)
'gold cat with a twitch' is the wordplay.
'gold' becomes 'Au' (Au is the chemical symbol for gold).
'cat' becomes 'tom' (a tom is a male cat).
'with' says to put letters next to each other.
'twitch' becomes 'tic' (tic is a kind of twitch).
'au'+'tom'+'a'+'tic'='AUTOMATIC'
'resembles a' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for automatic that I've seen before include "Type of gun or car" , "Instinctive or mechanical" , "by machine" , "lacking personal control" , "Functioning without human intervention" .)