The last one hundred in particular (7)
I believe the answer is:
finical
'particular' is the definition.
(thesaurus)
'the last one hundred in' is the wordplay.
'the last' becomes 'final' (I've seen this before**).
'one' becomes 'i' (Roman numeral).
'hundred' becomes 'c' (Roman numeral).
'in' means one lot of letters goes inside another.
'i'+'c'='ic'
'final' enclosing 'ic' is 'FINICAL'.
(Other definitions for finical that I've seen before include "Pernickety" , "Very fussy" .)