If Lars begs, Harry will get material for a surfboard (10)

I believe the answer is:

fibreglass

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

'material for a surfboard' is the definition.
I can't judge whether this defines the answer.

'if lars begs harry' is the wordplay.
'harry' indicates an anagram (harry can mean to attack or spoil).
'if'+'lars'+'begs'='iflarsbegs'
'iflarsbegs' anagrammed gives 'FIBREGLASS'.

'will get' is the link.

Can you help me to learn more?

(Another definition for fibreglass that I've seen is " Material used as insulation or to reinforce plastics".)

I've seen this clue in the Sydney Morning Herald.

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