Try to be seen in reflected light for practice (9)
I believe the answer is:
rehearsal
'for practice' is the definition.
(rehearsal is a kind of practice)
'try to be seen in reflected light' is the wordplay.
'try' becomes 'hear' (as in to try someone in court or hear their case).
'to be seen in' is an insertion indicator.
'reflected' shows that the letters should be reversed in order.
'light' becomes 'laser' (lasers are a type of light).
'laser' written backwards gives 'resal'.
'hear' placed within 'resal' is 'REHEARSAL'.
(Other definitions for rehearsal that I've seen before include "Practice session in preparation for public performance" , "Dry run" , "preparation in house?" , "show trial" , "Practice - run-through" .)