In the garden, they finish up with a number of insects (6)
I believe the answer is:
plants
'in the garden they' is the definition.
The definition suggests an adverb but the answer is not.
'finish up with a number of insects' is the wordplay.
'finish' indicates taking half.
'with' is an insertion indicator.
'a' becomes 'an'.
'number of insects' becomes 'lts' (I can't explain this - if you can you should give a lot more credence to this answer).
'up' cut in half is 'p'.
'an' put inside 'lts' is 'lants'.
'p'+'lants'='PLANTS'
Can you help me to learn more?
(Other definitions for plants that I've seen before include "Vegetable organisms" , "Living organisms without power of movement" , "Trees, shrubs etc." , "Settles" , "Places in the earth" .)