Figure a rail crash to bring a sort of infection (5)
I believe the answer is:
viral
'figure a' is the definition.
I can't judge whether this definition defines the answer.
'rail crash to bring a sort of infection' is the wordplay.
I cannot really understand how this works, but
an anagram of 'rail' is 'iral' which is located in the answer.
A single letter 'v' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for viral that I've seen before include "Like pathological agents" , "Like the common cold" , "as an internet sensation" , "Relating to a pathogenic agent of disease" , "(Of video) fast spreading" .)