Beast bound to appear after intermittent rain at sea (8)
I believe the answer is:
antelope
'beast' is the definition.
(I've seen this before)
'bound to appear after intermittent rain at sea' is the wordplay.
'bound' becomes 'lope' (to lope is to travel with bounding stride or bound**).
'to appear after' is a charade indicator (letters next to each other).
'intermittent' means one should take alternating letters.
'rain'+'at'+'sea'='rainatsea'
The alternating letters of 'rainatsea' are 'ante'.
'lope' after 'ante' is 'ANTELOPE'.
(Other definitions for antelope that I've seen before include "Horned animal" , "A swift-running animal like gazelle" , "Springbok, perhaps" , "Lean poet (anag.)" , "One petal for this animal" .)