Hesitant, worried about American fan (10)
I believe the answer is:
enthusiast
'fan' is the definition.
(I know that fan can be written as enthusiast)
'hesitant worried about american' is the wordplay.
'worried' indicates anagramming the letters (worry can mean to interfere with or disturb).
'about' indicates putting letters inside.
'american' becomes 'US' (United States).
'hesitant' is an anagram of 'enthiast'.
'enthiast' placed around 'us' is 'ENTHUSIAST'.
(Other definitions for enthusiast that I've seen before include "one not at all cool" , "buff" , "Ardent supporter" , "Devotee" , "Fan" .)