Bottle perhaps attached to optic? (5)
I believe the answer is:
Here is my best explanation:
This clue is a double definition.
'bottle' is the first definition.
'perhaps attached to optic?' is the second definition.
(Other definitions for nerve that I've seen before include "Grit", "Courage, like bodily fibre", "Bottle, courage", "Bodily fibre that communicates sensations", "Strand of body fibre", "Cord that carries instructions from brain to body", "Bundle of fibres < in face", "displaying self-possession", "Mettle, daring" and "Bodily fibre carrying sensation".)