Revolutionary shelter informer provided for marine plant (8)
I believe the answer is:
eelgrass
'for marine plant' is the definition.
(I've seen this before)
'revolutionary shelter informer' is the wordplay.
'revolutionary' shows that the letters should be reversed in order (letters revolve around).
'shelter' becomes 'lee' (as in lee side, the side sheltered from wind).
'informer' becomes 'grass' (grass can mean an informant).
'lee' reversed gives 'eel'.
'eel'+'grass'='EELGRASS'
'provided' is the link.
(Other definitions for eelgrass that I've seen before include "Submerged aquatic plant with ribbonlike leaves" , "Flowering plant of pondweed family" , "Marine plant" .)