It starts habitually and ends with (5)
I believe the answer is:
aitch
'it starts habitually and ends with' is the definition.
The definition suggests a singular noun which matches the answer.
This is all the clue.
Can you help me to learn more?
(Other definitions for aitch that I've seen before include "first bit of hymn?" , "character leading heroes" , "Eighth letter of the English alphabet" , "8th letter of the alphabet" , "that I will immediately succeed" .)