Tomorrow's headache, Matt? Member gone and Michael too - Labour's back! (8)
I believe the answer is:
hangover
'tomorrow's headache matt? member' is the definition.
I can't tell whether this definition defines the answer.
'gone and michael too labour's back' is the wordplay.
'gone' becomes 'han' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'and' says to put letters next to each other.
'michael' becomes 'Gove' (UK politician Michael Gove).
'too' says to put letters next to each other.
'back' says to take the final letters (the letter at the back).
The last letter of 'labour' is 'r'.
'han'+'gove'+'r'='HANGOVER'
Can you help me to learn more?
(Other definitions for hangover that I've seen before include "problem arising?" , "Morning after sickness?" , "After-effect of drinking spree" , "What one may have the morning after" , "Something that has survived from the past" .)