Insect starts to move over the heath (4)

I believe the answer is:

moth

'insect' is the definition.
(I know that moth is a type of lepidopterous insect)

'starts to move over the heath' is the wordplay.
'starts to' suggests taking the first letters.
The first letters of 'move over the heath' is 'MOTH'.

(Other definitions for moth that I've seen before include "Night flying insect" , "Fairy like 13" , "Lepidopteran" , "Night-flying insect" , "Cloth-eating insect" .)

I've seen this clue in The Sun.

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