Compete to win game maintaining initially professional attitude (9)
I believe the answer is:
Here is my best explanation:
'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'.
'towin' is an anagram of 'woint'.
'woint' placed around 'p' is 'wpoint'.
(Other definitions for viewpoint that I've seen before include "Slant", "stance", "Way of thinking", "Place from which to admire the scenery", "Attitude that determines outlook", "Opinion or position which is particularly good for admiring the scenery", "Stance", "way", "perspective" and "Good outlook here".)