Such a mammal’s position on a trail regularly overlooked (9)

I believe the answer is:

placental

'such a mammal's' is the definition.
(placental mammal is a kind of mammal)

'position on a trail regularly overlooked' is the wordplay.
'position' becomes 'place' (synonyms).
'regularly overlooked' means one should take alternating letters (letters removed at regular intervals).
'on'+'a'+'trail'='onatrail'
The alternating letters of 'onatrail' are 'ntal'.
'place'+'ntal'='PLACENTAL'

(Another definition for placental that I've seen is " Like a category of mammals".)

I've seen this clue in The Times.

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