Greatly affected writer kidnapped by shifty dude (7)
I believe the answer is:
upended
'greatly affected' is the definition.
The answer and definition are not the same part of speech. However, past participle verbs and adjectives can sometimes define each other.
'writer kidnapped by shifty dude' is the wordplay.
'writer' becomes 'pen' (something which writes).
'kidnapped by' is an insertion indicator.
'shifty' is an anagram indicator.
'dude' with letters rearranged gives 'uded'.
'pen' put within 'uded' is 'UPENDED'.
Can you help me to learn more?
(Other definitions for upended that I've seen before include "Inverted" , "Capsized" , "Turned upside down, topled" .)