She may open up when the lights are low (4)
I believe the answer is:
iris
'she' is the definition.
(I've seen this before)
'open up when the lights are low' is the wordplay.
I cannot quite see how this works, but
'up' could be 'is' (I've seen this in other clues) and 'is' is found in the answer.
This may be the basis of clue (or it may be nonsense).
'may' is the link.
Can you help me to learn more?
(Other definitions for iris that I've seen before include "Woman" , "plant with showy flowers" , "Plant - part of the eye" , "Part of the eye, usually brown or blue" , "bit of a looker" .)