In effect, a strange lustre (6)
I believe the answer is:
result
'in effect' is the definition.
'result' can be an answer for 'effect' (synonyms). I am unsure of the 'in' bit.
'a strange lustre' is the wordplay.
'a strange' indicates anagramming the letters.
'lustre' is an anagram of '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" .)