Thoughtfulness of Charlie on team, helping (13)
I believe the answer is:
consideration
'thoughtfulness' is the definition.
('consideration' can be a synonym of 'thoughtfulness')
'charlie on team helping' is the wordplay.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'team' becomes 'side' (I've seen this before**).
'helping' becomes 'ration' (I've seen this before).
'c'+'on'+'side'+'ration'='CONSIDERATION'
'of' is the link.
(Other definitions for consideration that I've seen before include "examination" , "Kindness" , "Bearing in mind - payment" , "Reward; careful thought" , "Thoughtfulness - relevant factor" .)