Heading off, tiny child initially sees spectacular chasm (5)

I believe the answer is:

abyss

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'chasm' is the definition.
(abyss is a kind of chasm)

I don't understand the remainder of the clue.

(Other definitions for abyss that I've seen before include "Hell; hole" , "great depth" , "Very large and deep chasm" , "Bottomless pit" , "Deep hole, seems bottomless" .)

I've seen this clue in The Times.

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