Quiet type who shows endurance — a ''sticker (7)
I believe the answer is:
plaster
'''sticker' is the definition.
(thesaurus)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for plaster that I've seen before include "Spread" , "Small wound covering" , "Wall surface" , "Stuff that sticks on ceilings or wounds" , "one sticking on through injury?" .)