Made up legend for one that's mostly relaxed (8)
I believe the answer is:
mythical
'made up' is the definition.
(thesaurus)
'legend for one that's mostly relaxed' is the wordplay.
'legend' becomes 'myth' (I've seen this before).
'for' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'that's mostly relaxed' becomes 'cal' (I can't justify this - if you can you should give a lot more credence to this answer).
'myth'+'i'+'cal'='MYTHICAL'
Can you help me to learn more?
(Other definitions for mythical that I've seen before include "Legendary" , "Based on traditional stories" , "Based on fable" , "Imaginary or based on folk tales" , "Existing in legends or traditional stories" .)