A student hugged by girl -- that's infectious (7)
I believe the answer is:
malaria
'that's infectious' is the definition.
I can't judge whether this defines the answer.
'a student hugged by girl' is the wordplay.
'student' becomes 'l' (as in L-plates for learner drivers).
'hugged by' means one lot of letters goes inside another (I've seen this in other clues).
'girl' becomes 'maria' ().
'a'+'l'='al'
'al' placed into 'maria' is 'MALARIA'.
Can you help me to learn more?
(Other definitions for malaria that I've seen before include "Tropical fever" , "Disease carried by mosquitos" , "Mosquito-transmitted disease" , "Disease from a mosquito bite" , "Disease causing fever transmitted by mosquitos" .)