Insects in season win out against arachnids (8)
I believe the answer is:
termites
'insects' is the definition.
(termite is a kind of insect)
'season win out against arachnids' is the wordplay.
'season win out' becomes 'ter' (I am not sure about this - if you are sure you should believe this answer much more).
'against' says to put letters next to each other.
'arachnids' becomes 'mites' (mite is a kind of arachnid).
'ter'+'mites'='TERMITES'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for termites that I've seen before include "Ant-like social insect that feeds on wood" , "Destructive workers" , "Ant-like insects that feed on wood" , "Flightless insects living in mounds" .)