City has energy-saving lights (5)
I believe the answer is:
leeds
'city' is the definition.
(city in England)
'energy-saving lights' is the wordplay.
I cannot quite see how this works, but
'energy' could be 'e' (physics symbol as in E=mc2) and 'e' is found within the answer.
The remaining letters 'leds' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'has' acts as a link.
Can you help me to learn more?
(Other definitions for leeds that I've seen before include "Northern town" , "City of northern England - castle of southern England" , "22 [FA CUP] runners-up" , "British city and premier division football club" , "City on River Aire" .)