... strong inclination to write plainsong (8)
I believe the answer is:
penchant
'strong inclination' is the definition.
(I've seen this in another clue)
'write plainsong' is the wordplay.
'write' becomes 'pen' (synonyms).
'plainsong' becomes 'chant' (I've seen this in another clue).
'pen'+'chant'='PENCHANT'
'to' acts as a link.
(Other definitions for penchant that I've seen before include "Inclination; taste" , "Predilection, preference" , "Partiality" , "'Predilection, a strong liking (8)'" , "Leaning towards or liking for" .)