Small fish tail from pilchard is hot accompaniment (4,4)
I believe the answer is:
side dish
'accompaniment' is the definition.
(I've seen this before)
'small fish tail from pilchard is hot' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'fish' becomes 'ide' (type of fish).
'tail from pilchard' becomes 'dis' (I can't explain this - if you can you should believe this answer much more).
'is hot' becomes 'h' (abbreviation eg on taps).
's'+'ide'+'dis'+'h'='SIDE-DISH'
Can you help me to learn more?
(Other definitions for side dish that I've seen before include "extra food" , "something extra, of course" , "It goes with a main course" , "Food item subordinate to the main one" , "Supplementary item at table" .)