Delta split coast (5)
I believe the answer is:
drift
'coast' is the definition.
(I've seen this before)
'delta split' is the wordplay.
'delta' becomes 'd' (phonetic alphabet: alpha, bravo, charlie etc.).
'split' becomes 'rift' (I've seen this before).
'd'+'rift'='DRIFT'
(Other definitions for drift that I've seen before include "Import" , "Move with wind and tide" , "Slide" , "Tendency" , "Gist - snow" .)