Popular chap at café finally serving porridge (6)
I believe the answer is:
inside
'serving porridge' is the definition.
(I've seen this before)
'popular chap at cafe finally' is the wordplay.
'popular' becomes 'in' (something that's 'in' is fashionable).
'chap' becomes 'sid' (man's name).
'at' says to put letters next to each other.
'finally' indicates one should take the final letters.
The final letter of 'cafe' is 'e'.
'in'+'sid'+'e'='INSIDE'
(Other definitions for inside that I've seen before include "Privileged" , "being held" , "confined" , "banged up" , "Within - interior" .)