Nerve (5)
'nerve' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for cheek that I've seen before include "Brass neck" , "Part of face or informal impudence" , "lip, or nearby part of head" , "Disrespectful talk" , "Chap" .)
'nerve' is the definition.
(optic nerve is a kind of nerve)
This is all the clue.
(Other definitions for optic that I've seen before include "Relating to the eyes" , "Related to sight" , "Pertaining to the eye" , "Spirit measuring device" , "What could measure the spirits" .)
'nerve' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for temerity that I've seen before include "Yet merit may lead to rashness" , "Overconfidence" , "Rashness, audacity" , "Impudence" , "Presumption" .)