Hoover perhaps swallowing brother's geranium (4,6)
I believe the answer is:
herb robert
'geranium' is the definition.
(herb robert is a kind of geranium)
'hoover perhaps swallowing brother's' is the wordplay.
'hoover perhaps' becomes 'herbert' (I can't justify this - if you can you should believe this answer much more).
'swallowing' is an insertion indicator.
'brother' becomes 'bro' (short for brother).
'herbert' enclosing 'bro' is 'HERB ROBERT'.
Can you help me to learn more?
(Other definitions for herb robert that I've seen before include "Wayside plant with small red flowers" , "Stinking cranesbill" , "A pungent cranesbill" .)