Small border that's rather like grass (5)
I believe the answer is:
sedge
'grass' is the definition.
(I've seen this before)
'small border' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'border' becomes 'edge' (synonyms).
's'+'edge'='SEDGE'
'that's rather like' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for sedge that I've seen before include "Grasslike marsh plant" , "Marsh grass" , "plant with triangular stems" , "Grass-like plant growing in wet places" , "Wetland grass-like plant" .)