Guys agree, stupidly, to adopt one group of animals (9)
I believe the answer is:
menagerie
'group of animals' is the definition.
'menagerie' can be an answer for 'animals' (I've seen this before). I'm not certain of the 'group of' bit.
'guys agree stupidly to adopt one' is the wordplay.
'guys' becomes 'men' (guy can mean a man).
'stupidly' indicates an anagram (a stupid ordering of the letters).
'to adopt' is an insertion indicator.
'one' becomes 'I' (Roman numeral).
'agree' is an anagram of 'agere'.
'agere' placed around 'i' is 'agerie'.
'men'+'agerie'='MENAGERIE'
Can you help me to learn more?
(Other definitions for menagerie that I've seen before include "collected animals" , "A collection of wild animals in captivity" , "place to keep animals" , "[TENNESSEE WILLIAMS] work in part" , "lots of animals" .)