E.g. setter's tight post-holiday state (4,9)
I believe the answer is:
dogs breakfast
'e g' is the definition.
I know nothing about this answer so I can't tell whether this works.
'setter's tight post-holiday state' is the wordplay.
'setter's' becomes 'dog's' (a setter is a type of dog).
'tight' becomes 'fast' (both can mean secure).
'post' is a charade indicator (letters next to each other) (post- can mean after).
'holiday state' becomes 'break' (I am not sure about this - if you are sure you should believe this answer much more).
'fast' put after 'break' is 'breakfast'.
'dogs'+'breakfast'='DOGS BREAKFAST'
Can you help me to learn more?
(Other definitions for dogs breakfast that I've seen before include "A job poorly executed" , "Mess (served to Fido?)" , "Untidy mess (to feed pet?)" , "Darkest of bags (anag)" , "Mess - pet food" .)