Reward thoughtfulness (13)
I believe the answer is:
consideration
This clue is a double definition.
'reward' is the first definition.
(thesaurus)
'thoughtfulness' is the second definition.
('consideration' can be a synonym of 'thoughtfulness')
(Other definitions for consideration that I've seen before include "Reward; careful thought" , "Study" , "Kindness" , "Bearing in mind - payment" , "A motive" .)