Strains of seaweeds with leaves (5)
I believe the answer is:
racks
'strains' is the definition.
(racking is a kind of straining)
'seaweeds with leaves' is the wordplay.
'seaweeds' becomes 'wracks' (wrack is a kind of seaweed).
'with' becomes 'w' (abbreviation).
'leaves' is a deletion indicator.
'wracks' with 'w' taken out is 'RACKS'.
'of' acts as a link.
(Other definitions for racks that I've seen before include "Frameworks for holding objects or for torture" , "Frameworks of shelving" , "Frameworks, for torture say" .)