Works out, when the snares set have caught nothing (7)
I believe the answer is:
reasons
'works out' is the definition.
The answer and definition can be both related to thinking as well as being verbs in their -s form.
Maybe there's an association between them I don't understand?
'the snares set have caught nothing' is the wordplay.
'set' is an anagram indicator (instruction to set the letters).
'have' is an insertion indicator.
'caught nothing' becomes 'o' (I can't justify this - if you can you should give a lot more credence to this answer).
'snares' anagrammed gives 'reasns'.
'reasns' placed around 'o' is 'REASONS'.
'when' acts as a link.
Can you help me to learn more?
(Other definitions for reasons that I've seen before include "Infers logically" , "Ness oar (anag.)" , "Rationalises" , "Rational motives" , "Motives, explanations" .)