Shout 'Slow down! Is emerald coating solidified? (12)
I believe the answer is:
crystallised
'solidified?' is the definition.
('solidified?'->'crystallized' is in my internal thesaurus and 'ize'->'ise')
'shout 'slow down is emerald coating' is the wordplay.
I cannot quite see how this works, but
'shout' could be 'cry' (synonyms) and 'cry' is found within the answer.
'down' could be 'd' and 'd' is located in the answer.
'is' is within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for crystallised that I've seen is " took shape".)