Being frailer, I fired weapon

I believe the answer is:

air rifle

I'm a little stuck... Click here to teach me more about this clue!

'weapon' is the definition.
(I've seen this before)

'being frailer i fired' is the wordplay.
'frailer i' can be anagrammed to 'AIR RIFLE'.
But, I am not clear how the anagram is indicated.

Can you help me to learn more?

(Other definitions for air rifle that I've seen before include "Shooting weapon" , "Fire liar (anag)" , "Pneumatic arm" , "Rail fire (anag) - weapon" , "Firearm" .)

I've seen this clue in The Telegraph.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.