Bone ultimately funny in arm (5)
I believe the answer is:
equip
'arm' is the definition.
(arm can mean to equip or supply)
'bone ultimately funny' is the wordplay.
'ultimately' says to take the final letters.
'funny' becomes 'quip' (both can mean a joke or witty remark).
The last letter of 'bone' is 'e'.
'e'+'quip'='EQUIP'
'in' is the link.
(Other definitions for equip that I've seen before include "Supply tools" , "Supply (with items)" , "Sally" , "Pique (anag.)" , "Arm" .)