Showing fellow having trouble with parasites — any number eradicated (13)
I believe the answer is:
manifestation
'showing' is the definition.
(thesaurus)
'fellow having trouble with parasites any number eradicated' is the wordplay.
'fellow' becomes 'man' (fellow can mean a man).
'having' means one lot of letters go next to another.
'trouble with parasites' becomes 'infestation' (eg a lice infestation).
'any number' becomes 'n' (mathematical symbol for an unspecified number).
'eradicated' suggests deleting specific letters.
'infestation' with 'n' taken out is 'ifestation'.
'man'+'ifestation'='MANIFESTATION'
(Other definitions for manifestation that I've seen before include "Sign" , "Ghostly appearance" , "Symptom (of an ailment)" , "Demonstration" , "Display" .)