Appreciation of sea air, occasionally (3)
I believe the answer is:
ear
'appreciation' is the definition.
(eg an 'ear for music' - ability to appreciate it)
'sea air occasionally' is the wordplay.
'occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
'sea'+'air'='seaair'
The alternate letters of 'seaair' are 'EAR'.
'of' acts as a link.
(Other definitions for ear that I've seen before include "Discernment musicians need" , "That makes sense" , "Auricle" , "good sense of music" , "Place for a plug" .)