Cleaning most of horses' feet by enclosure (9)
I believe the answer is:
hoovering
'cleaning' is the definition.
(hoovering is a kind of cleaning)
'most of horses' feet by enclosure' is the wordplay.
'most of' means to remove the last letter.
'horses' feet' becomes 'hooves' (I've seen this before).
'by' means one lot of letters go next to another.
'enclosure' becomes 'ring'.
'hooves' with its last letter removed is 'hoove'.
'hoove'+'ring'='HOOVERING'
(Other definitions for hoovering that I've seen before include "sucking up" , "Domestic chore" .)