More muscular appearance initially feeds one's strength (7)
I believe the answer is:
meatier
'more muscular' is the definition.
Both the definition and answer are comparative adjectives. Perhaps there's a link between them I don't understand?
'appearance initially feeds one's strength' is the wordplay.
'initially' says to take the initial letters.
'feeds' is an insertion indicator (one word is fed by another set of letters).
'one' becomes 'me' (a setter might use 'one' to humourously mean 'me').
'strength' becomes 'tier' (I am not sure about this - if you are sure you should believe this answer much more).
The initial letter of 'appearance' is 'a'.
'me'+'tier'='metier'
'a' inserted into 'metier' is 'MEATIER'.
Can you help me to learn more?
(Other definitions for meatier that I've seen before include "having more muscle" , "More brawny" , "Having more flesh" , "More substantial - emirate (anag)" .)