Character sometimes dropped, a sensation (5)
I believe the answer is:
aitch
'character' is the definition.
(the spelled out name of the letter H)
'a sensation' is the wordplay.
'sensation' becomes 'itch' (I can't explain this - if you can you should give a lot more credence to this answer).
'a'+'itch'='AITCH'
'sometimes dropped' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for aitch that I've seen before include "Aspirated letter" , "that I will immediately succeed" , "bone" , "Letter sound that's often dropped?" , "what some drop?" .)