City of steel also full of light (6)
I believe the answer is:
toledo
'city of steel' is the definition.
'Toledo' can be an answer for 'city' (Toledo is a Spanish city). I am not certain of the 'of steel' bit.
'also full of light' is the wordplay.
'also' becomes 'too' (synonyms).
'full of' is an insertion indicator.
'light' becomes 'led' (light-emitting diode).
'too' placed around 'led' is 'TOLEDO'.
Can you help me to learn more?
(Other definitions for toledo that I've seen before include "City in central Spain famous for swords" , "Spanish city known for swords" , "Tapering sword" , "Spanish city known for swordmaking" , "To dole out in the Spanish city" .)