Stiffly formal or cryptically relaxed from the start? (10)
I believe the answer is:
primordial
'from the start?' is the definition.
(primordial can mean early or prehistoric)
'stiffly formal or cryptically relaxed' is the wordplay.
'stiffly formal' becomes 'prim' (I've seen this in another clue).
'cryptically relaxed' becomes 'dial' (I can't justify this - if you can you should give a lot more credence to this answer).
'prim'+'or'+'dial'='PRIMORDIAL'
(Other definitions for primordial that I've seen before include "From the beginning of time" , "from the first" , "Existing from the start of time" , "Original" , "Having existed from the very start - limp or arid (anag)" .)