A hole that needs no peg in (7)

I believe the answer is:

opening

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

'a hole' is the definition.
(an opening is a hole or gap)

'needs no peg in' is the wordplay.
'no peg in' anagrams to 'OPENING'.
Though, I'm unsure how this is indicated.

'that' is the link.

Can you help me to learn more?

(Other definitions for opening that I've seen before include "- - time (pub)" , "Gateway - opportunity" , "Beginning; breach" , "Kicking off" , "Hole; beginning" .)

I've seen this clue in The Globe and Mail.

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