Gall, say, marketing with short weight included (8)
I believe the answer is:
swelling
'gall say' is the definition.
(gall is a type of swelling or growth)
'marketing with short weight included' is the wordplay.
'marketing with' becomes 'selling' (synonyms. I am not sure about the 'with' bit.).
'short weight' becomes 'w' (short for weight; 'short' indicates an abbreviation).
'included' is an insertion indicator.
'selling' enclosing 'w' is 'SWELLING'.
(Other definitions for swelling that I've seen before include "Abnormal enlargement" , "Tumour" , "Growth" , "area suffering inflation" , "increasing in volume" .)