__ Stains; Marks That Are Hard to Get Rid of

This page is the CodyCross answer for the clue below from Making a Documentary, Group 1516, Puzzle 4 (Light Reflector).

Question is: __ Stains; Marks That Are Hard to Get Rid of

and the answer is: STUBBORN

Word Meaning:

STUBBORN — Refusing to move or to change one's opinion; obstinate; firmly resisting; persistent in doing something.

Definitions from Wiktionary.