### Clue: Throw a square cut at source of radiation (6)
### Answer: QUASAR 
 ### Explanation: Definition: source of radiation
  **Anagram of**(throw) A SQUAR{"square" **minus** last letter(cut)}
Answer:  One of the objects believed to be the most distant (and hence oldest) and most luminous in the universe, compact sources of immense energy,radiation in the form of light, infrared, etc.  Short for "quasi-stellar radio source".