First musical gift in case, round one (8)
I believe the answer is:
earliest
'first' is the definition.
(similar in meaning)
'musical gift in case round one' is the wordplay.
'musical gift' becomes 'ear' (a talented musician has 'the ear').
'in case' becomes 'lest' (as in 'lest we forget').
'round' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'lest' enclosing 'i' is 'liest'.
'ear'+'liest'='EARLIEST'
(Other definitions for earliest that I've seen before include "Nearest the beginning in time" , "Next available" , "Arriving first" , "Soonest" , "The first to arrive - to get the worm?" .)