Both initials of Salvation Army on left shoe (6)

I believe the answer is:

sandal

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'shoe' is the definition.
(I know that sandal is a type of shoe)

'both initials of salvation army on left' is the wordplay.
'both initials of' becomes 'nda' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'salvation army' becomes 'SA' (abbreviation).
'on' is a charade indicator (letters next to each other).
'left' becomes 'l' (common abbreviation).
'nda' put after 'sa' is 'sanda'.
'sanda'+'l'='SANDAL'

Can you help me to learn more?

(Other definitions for sandal that I've seen before include "Openwork shoe" , "Wood" , "Light footwear" , "Light open-toed shoe" , "Light strapped shoe" .)

I've seen this clue in The Telegraph.

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