This writer's indeed including German figures of speech (7)
I believe the answer is:
imagery
'figures of speech' is the definition.
(I've seen this before)
'this writer's indeed including german' is the wordplay.
'this writer's' becomes 'I'm' ('I am' referring to the writer of the clue).
'indeed' becomes 'ay' ('ay' and 'aye' can mean yes).
'including' means one lot of letters goes inside another.
'german' becomes 'ger' (abbreviation).
'ay' enclosing 'ger' is 'agery'.
'im'+'agery'='IMAGERY'
(Other definitions for imagery that I've seen before include "Figurative language, eg, in poem" , "paintings" , "something easy to see?" , "Descriptive language" , "Use of language to produce pictures in the mind" .)