Toy gun found by base of target (6)
I believe the answer is:
trifle
'toy' is the definition.
(thesaurus)
'gun found by base of target' is the wordplay.
'gun' becomes 'rifle' (rifle is a kind of gun).
'found by' means one lot of letters go next to another.
'base of' says to take the final letters.
The last letter of 'target' is 't'.
'rifle' after 't' is 'TRIFLE'.
(Other definitions for trifle that I've seen before include "Act foolishly" , "nothing?" , "Dessert - something unimportant" , "Amuse oneself" , "Knick-knack" .)