Top viral infection expert achieving through chance (7)
I believe the answer is:
fluking
'top viral' is the definition.
I can't tell whether this definition defines the answer.
'infection expert achieving through chance' is the wordplay.
I cannot quite understand how this works, but
'infection' could be 'flu' (I've seen this before) and 'flu' is found in the answer.
'through' could be 'in' and 'in' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for fluking that I've seen is " Succeeding by chance".)