The most common and most likely answer to this crossword clue is the 4 plus 3 letter word IRON AGE
I've seen this crossword clue in The Daily Telegraph
I
R
O
N
A
G
E
More clues leading to the result IRON AGE
- Resolution of mostly regional division amongst archaeologists
- Not when the golf club was fashionable, though
- Wrath surrounding old scold for period
- A long time redeveloping a region
- Press agent primarily recalled for one period of change
- Irish cardinal collecting silver for a time
- Irish cardinal hoarding silver for a time
- I led Orange Revolution in historical period
- Smooth, mature — when 16a discovered heavy metal
- Time of endless dry wit — a good experience at first
Buddy explains!
The straight part
We know that "when 16a discovered heavy metal" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case when 16a discovered heavy metal = iron age.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.