To some extent, full-time gaming is very good (4)
I believe the answer is:
mega
'very good' is the definition.
(informal term for excellent)
'to some extent full-time gaming' is the wordplay.
'to some extent' says the answer is hidden in the clue (I've seen 'extent of' mean this (I've seen this in other clues)).
'MEGA' can be found hidden inside 'full time gaming'.
'is' acts as a link.
(Other definitions for mega that I've seen before include "'Excellent, colloquially (4)'" , "Very large (prefix)" , "As brilliant" , "Very large (colloq.)" , "Big" .)