Lot of junk is metal (6)
I believe the answer is:
kismet
'lot' is the definition.
(I've seen this before)
'of junk is metal' is the wordplay.
'of' indicates the answer is hidden within the clue.
'KISMET' is hidden in the letters of 'junk is metal'.
(Other definitions for kismet that I've seen before include "Fate - 1953 musical" , "Destiny; 50s musical" , "lot in life" , "Broadway musical" , "Turkish fate, destiny" .)