What looks infectious, making you attractive? (3-8)
I believe the answer is:
eye-catching
'attractive?' is the definition.
(I've seen this before)
'what looks infectious' is the wordplay.
'what looks' becomes 'eye' (organ which looks).
'infectious' becomes 'catching' (similar in meaning).
'eye'+'catching'='EYE-CATCHING'
'making you' is the link.
(Other definitions for eye-catching that I've seen before include "Attracting attention" , "Conspicuous" , "Attractive" , "Standing out" , "Striking" .)