Weapon's look not good (5)
I believe the answer is:
lance
'weapon's' is the definition.
(lance is a kind of weapon)
'look not good' is the wordplay.
I cannot really understand how this works, but
'look' could be 'la' (I've seen this in other clues) and 'la' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for lance that I've seen before include "Spear carried by mounted soldier" , "Long, pointed weapon (5)." , "Incise" , "Shafted weapon used on horseback" , "Rider's long weapon" .)