She dabbled with TNT in decimal quantities (6)
I believe the answer is:
tenths
'she dabbled' is the definition.
I can't tell whether this defines the answer.
'with tnt in decimal quantities' is the wordplay.
'with' means one lot of letters go next to another.
'tnt in decimal' becomes 'tent' (I can't justify this - if you can you should believe this answer much more).
'quantities' becomes 'Hs' (H is an example).
'tent' next to 'hs' is 'TENTHS'.
Can you help me to learn more?
(Other definitions for tenths that I've seen before include "Tithes" , "Small portions" , "tiny portions" , "Sections" .)