Strange, strange, strange: ultimately CO (8)
I believe the answer is:
sergeant
'co' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'strange strange strange ultimately' is the wordplay.
'strange' indicates anagramming the letters.
'ultimately' suggests the final letters.
The final letter of 'strange' is 'e'.
'strange'+'e'='strangee'
'strangee' is an anagram of 'SERGEANT'.
(Other definitions for sergeant that I've seen before include "one with stripes" , "Reagents (anag)" , "Reagents for army NCO" , "NCO or police officer ..." , "Police rank" .)