Breathy line in chat, perhaps (5)
I believe the answer is:
aitch
'breathy line in chat perhaps' is the definition.
I can't judge whether this defines the answer.
'line in chat perhaps' is the wordplay.
'line' becomes 'i' (I am not sure about this - if you are sure you should believe this answer much more).
'in' is an insertion indicator.
'perhaps' indicates an anagram.
'chat' with letters rearranged gives 'atch'.
'i' inserted into 'atch' is 'AITCH'.
Can you help me to learn more?
(Other definitions for aitch that I've seen before include "what some drop?" , "the start of hives?" , "first bit of hymn?" , "8th letter of the alphabet" , "It's dropped by Cockneys" .)