Soft, that is, though it may be crusty (3)
I believe the answer is:
pie
'it may be crusty' is the definition.
The definition suggests a singular noun which matches the answer.
'soft that is' is the wordplay.
'soft' becomes 'p' (musical abbreviation for 'piano').
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'p'+'ie'='PIE'
'though' acts as a link.
Can you help me to learn more?
(Other definitions for pie that I've seen before include "what to cook for dinner?" , "bakery item" , "Anna's constituent" , "Covered tart" , "Very easy answer as" .)