Whimsically perhaps writing to Charlie - rambling, flamboyant in style (10)
I believe the answer is:
rhetorical
'flamboyant in style' is the definition.
'rhetorical' can be an answer for 'flamboyant' (thesaurus). I'm not sure about the 'in style' bit.
'whimsically perhaps writing to charlie rambling' is the wordplay.
I cannot really see how this works, but
'writing' could be 'r' (one of the traditional three R's of education) and 'r' is located in the answer.
'to' is present in the answer.
an anagram of 'charlie' is 'herical' which is within the remaining letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for rhetorical that I've seen before include "Over-elaborate in style" , "using words extravagantly" , "Relating to persuasive speaking" , "in speech" , "Sort of question" .)