Sort of hammer everyone's come across outside (6)
I believe the answer is:
mallet
'sort of hammer' is the definition.
'everyone's come across outside' is the wordplay.
'everyone' becomes 'all' (all people).
'come across' becomes 'met' (I can't explain this - if you can you should give a lot more credence to this answer).
'outside' indicates putting letters inside (some letters go outside others).
'all' placed within 'met' is 'MALLET'.
Can you help me to learn more?
(Other definitions for mallet that I've seen before include "Hammer for pegs or croquet" , "stick in Polo" , "Wooden-headed hammer" , "Wooden hammer used in polo" , "Hitting tool" .)