Regressing, until I snottily coughed out lump of tissue (6)
I believe the answer is:
tonsil
'lump of tissue' is the definition.
'tonsil' can be an answer for 'tissue' (tonsil is a kind of tissue). I'm not certain of the 'lump of' bit.
'regressing until i snottily coughed out' is the wordplay.
'regressing' shows that the letters should be reversed in order (to regress is to go backwards).
'out' indicates a hidden word (I've seen 'out of' mean this).
'lisnot' is hidden in the letters of 'until i snottily coughed'.
'lisnot' in reverse letter order is 'TONSIL'.
Can you help me to learn more?
(Other definitions for tonsil that I've seen before include "One of two pieces of tissue on the pharynx" , "Mass of tissue" , "organ" , "Tissue at back of throat" , "One often removed" .)