Moderate felt neglected, somewhat upset (6)
I believe the answer is:
gentle
'moderate' is the definition.
(I've seen this in another clue)
'felt neglected somewhat upset' is the wordplay.
'somewhat' indicates the answer is hidden within the clue.
'upset' is a reversal indicator.
'eltneg' is hidden in the letters of 'felt neglected'.
'eltneg' in reverse letter order is 'GENTLE'.
(Other definitions for gentle that I've seen before include "Mild; a maggot" , "'Do not go . . . . . . into that good night' (Dylan Thomas)" , "amiable" , "Mild-mannered" , "Kind-natured" .)