Letter also featured in amusing write-up? (8)
I believe the answer is:
landlord
'letter' is the definition.
(I've seen this before)
'also featured in amusing write-up?' is the wordplay.
'also' becomes 'and' (both can mean in addition).
'featured in' means one lot of letters goes inside another.
'amusing' becomes 'droll' (I've seen this before).
'write up?' says the letters should be written backwards (I've seen 'wrote up' mean this).
'droll' back-to-front is 'llord'.
'and' going into 'llord' is 'LANDLORD'.
(Other definitions for landlord that I've seen before include "Publican" , "Property owner who leases to others" , "Mein host" , "One who rents out property" , "He wants letters" .)