Small borders for plants (6)
I believe the answer is:
sedges
'plants' is the definition.
The answer is an example.
'small borders' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'borders' becomes 'edges' ('edge' can be a synonym of 'border').
's'+'edges'='SEDGES'
'for' acts as a link.
(Other definitions for sedges that I've seen before include "Rush-like plants growing in wet places" , "Flies" .)