Creature in love depressed by case of rash (5)
I believe the answer is:
rhino
'creature' is the definition.
(short for rhinoceros)
'in love depressed by case of rash' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'depressed by' says to put letters next to each other (in a down clue, some letters go below others).
'case of' means to remove the middle letters (outsides of).
'rash' with its centre taken out is 'rh'.
'in'+'o'='ino'
'ino' put after 'rh' is 'RHINO'.
(Other definitions for rhino that I've seen before include "one might charge in Africa" , "Large animal (abbr) - money (slang)" , "When provoked, one may charge" , "In brief, a large horned African animal" , "Dosh (slang)" .)