Insufficient amount from a Thermos, cast agreed (5,7)

I believe the answer is:
short measure
'insufficient amount' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'a thermos cast agreed' is the wordplay.
'cast' indicates an anagram (letters are dispersed or cast around).
'agreed' becomes 'sure' (I've seen this before).
'a'+'thermos'='athermos'
'athermos' anagrammed gives 'shortmea'.
'shortmea'+'sure'='SHORT MEASURE'
'from' is the link.
Can you help me to learn more?
(Another definition for short measure that I've seen is " Less than paid for".)
