Maiden applied thought (5)
I believe the answer is:
mused
'thought' is the definition.
(musing is a kind of thinking)
'maiden applied' is the wordplay.
'maiden' becomes 'm' (cricket abbreviation).
'applied' becomes 'used' ('use' can be a synonym of 'apply').
'm'+'used'='MUSED'
(Other definitions for mused that I've seen before include "Closer" , "Fuddled" , "Was absorbed in thought" , "Contemplated" , "'Meditated, mulled (5)'" .)