In a snorkel, perhaps, one may find seaweed (4)
I believe the answer is:
kelp
'seaweed' is the definition.
(I've seen this before)
'in a snorkel perhaps one may' is the wordplay.
'in' indicates the answer is hidden within the clue.
'KELP' is hidden in the letters of 'snorkel perhaps may'.
'find' acts as a link.
(Other definitions for kelp that I've seen before include "Large brown leathery seaweed" , "Type of finch" , "Type of seaweed" , "Coarse brown seaweed" , "Brown seaweed with fluted leathery fronds" .)