Oojamaflip, insubstantial and tacky (9)
I believe the answer is:
thingummy
'oojamaflip' is the definition.
(I've seen this before)
'insubstantial and tacky' is the wordplay.
'insubstantial' becomes 'thin' (I've seen this in another clue).
'and' means one lot of letters go next to another.
'tacky' becomes 'gummy' (I can't explain this - if you can you should believe this answer much more).
'thin'+'gummy'='THINGUMMY'
Can you help me to learn more?
(Other definitions for thingummy that I've seen before include "what's-its-name" , "Unidentified object" , "unknown object" , "whose name one's forgotten" , "Whatsit" .)