More beefy mass, one consumed by consumer (7)
I believe the answer is:
Here is my best explanation:
'more beefy' is the definition.
Both the definition and answer are comparative adjectives. Maybe you can see an association between them that I don't see?
'mass one consumed by consumer' is the subsidiary indication.
'mass' becomes 'm' (symbol used in Physics e.g. f=ma).
'one' becomes 'i' (Roman numeral).
'consumed by' means one lot of letters goes inside another.
'consumer' becomes 'eater' (eater is a kind of consumer).
'i' placed into 'eater' is 'eatier'.
(Other definitions for meatier that I've seen before include "More brawny", "having more muscle", "More substantial - emirate (anag)" and "Having more flesh".)