Metal tip – lead? (9)
I believe the answer is:
spearhead
'lead?' is the definition.
(I know that spearhead is a more specific form of lead)
'metal tip' is the wordplay.
'metal' becomes 'spear' (I can't explain this - if you can you should give a lot more credence to this answer).
'tip' becomes 'head' (head is a kind of tip).
'spear'+'head'='SPEARHEAD'
Can you help me to learn more?
(Other definitions for spearhead that I've seen before include "Leading force in a military attack" , "Part of weapon possibly iron" , "Advanced troops" , "front" , "initiate attack" .)