Sub weapon to Pedro, perhaps (7)
I believe the answer is:
torpedo
'sub weapon' is the definition.
(I've seen this in another clue)
'to pedro perhaps' is the wordplay.
'perhaps' is an anagram indicator.
'pedro' anagrammed gives 'rpedo'.
'to'+'rpedo'='TORPEDO'
(Other definitions for torpedo that I've seen before include "ruin" , "Underwater bomb" , "Missile form a submarine" , "Missile fired from underwater submarine" , "Trooped off with undersea missile" .)