Sketch liberal found in offensive, juvenile annual? (8)
I believe the answer is:
plantlet
'annual?' is the definition.
I know nothing about this answer so I can't tell whether this works.
'sketch liberal found in offensive juvenile' is the wordplay.
'sketch' becomes 'plan' (I've seen this in another clue).
'liberal' becomes 'l' (abbreviation).
'found in' is an insertion indicator.
'offensive juvenile' becomes 'tet' (I am not sure about this - if you are sure you should believe this answer much more).
'l' placed into 'tet' is 'tlet'.
'plan'+'tlet'='PLANTLET'
Can you help me to learn more?
(Another definition for plantlet that I've seen is " Small growth".)