Compete to win game maintaining initially professional attitude (9)
I believe the answer is:
viewpoint
'attitude' is the definition.
(viewpoint is a kind of attitude)
'compete to win game maintaining initially professional' is the wordplay.
'compete' becomes 'vie' ('vie' can be a synonym of 'compete'**).
'game' indicates an anagram (solving anagrams is a game).
'maintaining' is an insertion indicator.
'initially' suggests taking the first letters.
The first letter of 'professional' is 'p'.
'to'+'win'='towin'
'towin' is an anagram of 'woint'.
'woint' placed around 'p' is 'wpoint'.
'vie'+'wpoint'='VIEWPOINT'
(Other definitions for viewpoint that I've seen before include "Stance" , "Opinion or position which is particularly good for admiring the scenery" , "Slant" , "Attitude that determines outlook" , "Way of thinking" .)