In effect, a strange lustre (6)
I believe the answer is:
result
'in effect' is the definition.
'result' can be an answer for 'effect' (I have seen 'Effect of lustre ' mean 'result' so perhaps 'effect' could also mean 'result'). I'm not sure about the 'in' bit.
'a strange lustre' is the wordplay.
'a strange' indicates anagramming the letters.
'lustre' with letters rearranged gives 'RESULT'.
Can you help me to learn more?
(Other definitions for result that I've seen before include "Verdict" , "Final score" , "Effect of lustre" , "Final outcome" , "Effect - outcome" .)