Reflecting some merit, lasses feature on Scottish flag! (7)
I believe the answer is:
saltire
'scottish flag' is the definition.
(saltire can mean the flag of Scotland)
'reflecting some merit lasses feature' is the wordplay.
'reflecting' says the letters should be written in reverse.
'feature' says the answer is hidden in the clue (I've seen 'featuring' mean this).
'eritlas' is hidden within 'some merit lasses'.
'eritlas' back-to-front is 'SALTIRE'.
'on' acts as a link.
(Other definitions for saltire that I've seen before include "The Scottish flag" , "flag - 8's? [SAINT ANDREW]" , "X-shaped cross" , "Heraldic cross" , "Scottish cross" .)