Choice made by one Anglican is sharp and useful given frosty atmosphere (7)
I believe the answer is:
icepick
'sharp and useful given frosty atmosphere' is the definition.
I can't tell whether this definition defines the answer.
'choice made by one anglican' is the wordplay.
'choice' becomes 'pick' (synonyms).
'made by' says to put letters next to each other (letters written or made by another set of letters).
'one' becomes 'i' (Roman numeral).
'anglican' becomes 'ce' (Church of England).
'i'+'ce'='ice'
'pick' put after 'ice' is 'ICEPICK'.
'is' is the link.
Can you help me to learn more?
(Another definition for icepick that I've seen is " Weapon that killed Trotsky".)