Parasite reportedly shows strength (5)
I believe the answer is:
might
'strength' is the definition.
(I know that might is a type of strength)
'parasite reportedly' is the wordplay.
'parasite' becomes 'mite' (I've seen this in another clue).
'reportedly' shows a homophone (sound like).
'mite' sounds like 'MIGHT'.
'shows' is the link.
(Other definitions for might that I've seen before include "- - and main" , "Great power, strength" , "Doubtful" , "word expressing possibility" , "Strength - could possibly" .)