Relaxed in some rough seas, edgy at first (5)
I believe the answer is:
eased
'relaxed' is the definition.
(I've seen this before)
'in some rough seas edgy at first' is the wordplay.
'in' is an insertion indicator.
'some' becomes 'ed' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'rough' indicates anagramming the letters (a rough or broken ordering of the letters).
'first' suggests taking the first letters.
The initial letters of 'seas edgy at' is 'sea'.
'sea' is an anagram of 'ase'.
'ed' going around 'ase' is 'EASED'.
Can you help me to learn more?
(Other definitions for eased that I've seen before include "Given relief" , "rested" , "relented" , "Relaxed" , "Helped" .)