Seaweed carried by coastal gatherers (4)
I believe the answer is:
alga
'seaweed' is the definition.
(I've seen this before)
'carried by coastal gatherers' is the wordplay.
'carried by' says the answer is hidden in the clue.
'ALGA' is hidden within 'coastal gatherers'.
(Other definitions for alga that I've seen before include "Water plant with no stem or leaves" , "from ore found locally" , "nuisance on the beach?" , "Kind of seaweed" , "Irish moss, for example" .)