Turnbull returns to power - it's illuminating! (4)
I believe the answer is:
lamp
'it's illuminating' is the definition.
(I've seen this in another clue)
'turnbull returns to power' is the wordplay.
'turnbull' becomes 'mal' (I can't explain this - if you can you should believe this answer much more).
'returns' shows that the letters should be reversed in order.
'to power' becomes 'p' (symbol in physics).
'mal' backwards is 'lam'.
'lam'+'p'='LAMP'
Can you help me to learn more?
(Other definitions for lamp that I've seen before include "punch" , "Appliance producing light" , "Source of light, usually portable" , "Artificial source of illumination" , "Source of artificial light" .)