Hopalong Cassidy's sidekick (3)

I believe the answer is:

pal

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

'sidekick' is the definition.
('pal' can be a synonym of 'sidekick')

'hopalong cassidy's' is the wordplay.
'PAL' is hidden within the letters.
However, I am uncertain how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for pal that I've seen before include "Mate, buddy" , "Bud" , "Friend (colloq.)" , "Mate, informal friend" , "China" .)

I've seen this clue in the Evening Standard.

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