Like "first” and "second” (7)
I believe the answer is:
ordinal
'like first and second' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ordinal that I've seen before include "E.g. first" , "Of position in series; service book (hist.)" , "Relating to series order" , "Relating to position in a sequence" , "Numeral indicating rank order" .)