Scrounger having caught fish returned horse (5)
I believe the answer is:
leech
'scrounger' is the definition.
(I've seen this before)
'caught fish returned horse' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'fish' becomes 'eel' (eel is a kind of fish).
'returned' says the letters should be written in reverse.
'horse' becomes 'H' (synonyms).
'c'+'eel'='ceel'
'ceel' reversed gives 'leec'.
'leec'+'h'='LEECH'
'having' is the link.
(Other definitions for leech that I've seen before include "Parasite - hanger-on" , "Old doctor" , "One used to bleed" , "Annelid worm, used in medicine of old" , "Blood-sucking worm or parasitical person" .)