Waxy substance, resin, alongside rigs at sea (9)
I believe the answer is:
ambergris
'waxy substance' is the definition.
(waxy substance produced by sperm whales)
'resin alongside rigs at sea' is the wordplay.
'resin' becomes 'amber' (amber is a kind of resin).
'alongside' says to put letters next to each other.
'at sea' indicates anagramming the letters.
'rigs' with letters rearranged gives 'gris'.
'amber'+'gris'='AMBERGRIS'
(Other definitions for ambergris that I've seen before include "A waxy substance" , "Sperm whale secretion used in perfumes" , "Ash-grey, scented substance obtained from whales" , "Sperm whale product used in perfumery" , "Substance from whales used in perfumes" .)