Game held up with fellow needing immediate attention (6)
I believe the answer is:
urgent
'needing immediate attention' is the definition.
(I've seen this in another clue)
'game held up with fellow' is the wordplay.
'game' becomes 'RU' (rugby union).
'held up' says the letters should be written in reverse.
'with' says to put letters next to each other.
'fellow' becomes 'gent' (synonyms).
'ru' in reverse letter order is 'ur'.
'ur'+'gent'='URGENT'
(Other definitions for urgent that I've seen before include "Pressing, compelling" , "Calling for immediate attention" , "Pressing, burning" , "In need of immediate action" , "grave?" .)