Calm down relative consuming drink both ends of day (6,2)
I believe the answer is:
steady on!
'calm down' is the definition.
(I've seen this before)
'relative consuming drink both ends of day' is the wordplay.
I cannot quite see how this works, but
'drink' could be 'tea' (tea is a drink) and 'tea' is present in the answer.
'of' could be 'o' and 'o' is present in the answer.
'day' could be 'd' (abbreviation for day) and 'd' is found within the answer.
The remaining letters 'syn' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for steady on! that I've seen before include "No set day (anag) -- keep calm!" , "Take it easy, slow down" , "Be more reasonable!" , "Slow down, stop there" .)