Noble king penetrates resistance (7)
I believe the answer is:
marquis
'noble' is the definition.
(marquis is a kind of noble)
'king penetrates resistance' is the wordplay.
'king' becomes 'r' (r is abbreviation for rex).
'penetrates' is an insertion indicator.
'resistance' becomes 'maquis' (Maquis is an example).
'r' placed within 'maquis' is 'MARQUIS'.
(Other definitions for marquis that I've seen before include "Nob" , "Noble, above count" , "Foreign nobleman ranking above a count" , "Continental aristocrat" , "De Sade's title" .)