Desperate chap bitten by dog perhaps a former teacher (6)
I believe the answer is:
pedant
'a former teacher' is the definition.
'pedant' can be an answer for 'teacher' (I have seen 'Old teacher' mean 'pedant' so perhaps 'teacher' could also mean 'pedant'). I'm unsure of the 'a former' bit.
'desperate chap bitten by dog' is the wordplay.
'desperate chap' becomes 'dan' (Desperate Dan is a comic book character).
'bitten by' means one lot of letters goes inside another (I've seen this in other clues).
'dog' becomes 'pet' (dogs are often kept as pets).
'dan' going within 'pet' is 'PEDANT'.
'perhaps' is the link.
Can you help me to learn more?
(Other definitions for pedant that I've seen before include "One pays undue attention to the petty details" , "Nitpicker" , "Academically fussy person" , "Fussy schoolmaster, academic" , "One is overly-concerned with detail" .)