In cracked ice, keep supple (7)
I believe the answer is:
elastic
'supple' is the definition.
(thesaurus)
'in cracked ice keep' is the wordplay.
'in' is an insertion indicator.
'cracked' indicates anagramming the letters.
'keep' becomes 'last' (I can't justify this - if you can you should believe this answer much more).
'ice' anagrammed gives 'eic'.
'eic' enclosing 'last' is 'ELASTIC'.
Can you help me to learn more?
(Other definitions for elastic that I've seen before include "Stretch material" , "Flexible, adaptable" , "Cats lie (anag.)" , "Stuff that stretches to Castile" , "Castile (anag)" .)