Large crowd heard in front of giant billboard (8)

I believe the answer is:

hoarding

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'billboard' is the definition.
(synonyms)

'large crowd heard in front of giant' is the wordplay.
'large crowd' becomes 'horde' (I've seen this in another clue).
'heard' shows a homophone (sound like).
'in front of giant' becomes 'ing' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'horde' is a homophone of 'hoard'.
'hoard'+'ing'='HOARDING'

Can you help me to learn more?

(Other definitions for hoarding that I've seen before include "Large outdoor signboard" , "screen of boards" , "space for posters here?" , "Board for ads" , "Setting great store" .)

I've seen this clue in The Telegraph.

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