What secures arm in place for drawing? (7)

I believe the answer is:

holster

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

'place for drawing?' is the definition.
(I've seen this in another clue)

I cannot understand how the rest of the clue works.

(Other definitions for holster that I've seen before include "Pistol case" , "put gun away" , "Pistol sheath" , "armrest" , "Pistol-holder" .)

I've seen this clue in The Telegraph.

Want a hint initially instead of a full solution? Install my app