Shrub to finish amongst seaweed (8)
I believe the answer is:
'shrub' is the definition.
(lavender is a kind of shrub)
'finish amongst seaweed' is the wordplay.
'finish' becomes 'end' (synonyms).
'amongst' indicates putting letters inside (I've seen this in other clues).
'seaweed' becomes 'laver' (I have seen 'Edible seaweed ' mean 'laver' so perhaps 'seaweed' could also mean 'laver').
'end' inserted into 'laver' is 'LAVENDER'.
'to' is the link.
(Other definitions for lavender that I've seen before include "Plant with aromatic mauve flowers" , "Fragrant, blue-flowered shrub" , "Pale lilac" , "Mauve flower, cultivated for its fragrant oil" , "shade" .)