Act irresponsibly with end of elephant gun (6)
I believe the answer is:
trifle
'act irresponsibly' is the definition.
'trifle' can be an answer for 'act' (trifling is a kind of acting). I'm unsure of the 'irresponsibly' bit.
'with end of elephant gun' is the wordplay.
'with' means one lot of letters go next to another.
'end of' suggests the final letters.
'gun' becomes 'rifle' (rifle is a kind of gun).
The last letter of 'elephant' is 't'.
't'+'rifle' is 'TRIFLE'.
Can you help me to learn more?
(Other definitions for trifle that I've seen before include "Possible component of meal" , "A desert of no importance" , "A bit" , "Filter (anag.)" , "Mess" .)