Sentimental work penned by MI6 man? (5)
I believe the answer is:
soppy
'sentimental' is the definition.
(I've seen this before)
'work penned by mi6 man?' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'penned by' means one lot of letters goes inside another.
'mi6 man?' becomes 'spy'.
'op' going into 'spy' is 'SOPPY'.
(Other definitions for soppy that I've seen before include "Mawkish" , "Feebly sentimental" , "Indulgently sentimental" , "Overemotional" , "Wet; sentimental" .)