Thieves indicated retro utensil was given to former British monarch by son (7)
I believe the answer is:
looters
'thieves' is the definition.
(I know this)
'indicated retro utensil was given to former british monarch by son' is the wordplay.
I cannot quite see how this works, but
'monarch' could be 'er' (abbreviation for Elizabeth Regina, British Queen) and 'er' is found within the answer.
'son' could be 's' (genealogical abbreviation for son) and 's' is located in the answer.
The remaining letters 'loot' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for looters that I've seen before include "They steal during riots" , "Plunderers" , "Pillagers, freebooters" .)