Small fragment is missing lead for Lewis, TV detective (5)
I believe the answer is:
morse
'tv detective' is the definition.
(Inspector Morse)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for morse that I've seen before include "Kind of code" , "One who enjoyed solving code" , "Oxford detective" , "Code inventor, Samuel" , "TV inspector" .)