Give an opinion about a lake like a gemstone (7)
I believe the answer is:
opaline
'lake like a gemstone' is the definition.
I can't judge whether this definition defines the answer.
'give an opinion about a' is the wordplay.
'give an opinion' becomes 'pali' (I can't explain this - if you can you should give a lot more credence to this answer).
'about' means one lot of letters goes inside another.
'a' becomes 'one'.
'pali' inserted within 'one' is 'OPALINE'.
Can you help me to learn more?
(Other definitions for opaline that I've seen before include "Semi-translucent glass" , "not entirely clear" , "white!" , "Translucent glass" , "gem-like quality" .)