Is the fellow inside sure it will be too much? (7)
I believe the answer is:
surfeit
'too much?' is the definition.
'is the fellow inside sure it' is the wordplay.
'is the fellow' becomes 'f' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'inside' means one lot of letters goes inside another.
'f' placed inside 'sure' is 'surfe'.
'surfe'+'it'='SURFEIT'
'will be' acts as a link.
Can you help me to learn more?
(Other definitions for surfeit that I've seen before include "Excess, glut" , "excessive amount" , "Fustier (anag)" , "Superabundance" , "it's more than one needs" .)