Type that is wearing glasses (7)
I believe the answer is:
species
'type' is the definition.
(I've seen this before)
'that is wearing glasses' is the wordplay.
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'wearing' means one lot of letters goes inside another.
'glasses' becomes 'specs' (spectacles).
'ie' going inside 'specs' is 'SPECIES'.
(Other definitions for species that I've seen before include "Group of organisms" , "Taxonomic group capable of interbreeding" , "Taxonomic grouping" , "Kind, sort" , "Sort, type" .)