Fellow working in health spa with name is brief success? (5,2,3,3)
I believe the answer is:
flash in the pan
'brief success?' is the definition.
(I've seen this in another clue)
'fellow working in health spa with name' is the wordplay.
'fellow' becomes 'f' (abbreviation - of a society etc.).
'working' indicates anagramming the letters.
'with' means one lot of letters go next to another.
'name' becomes 'n' (common abbreviation e.g. on forms).
'in'+'health'+'spa'='inhealthspa'
'inhealthspa' anagrammed gives 'lashinthepa'.
'f'+'lashinthepa'+'n'='FLASH IN THE PAN'
'is' is the link.
(Other definitions for flash in the pan that I've seen before include "Ephemeral success" , "Nine days' wonder" , "Brief success - flambe moment?" , "Nine-days wonder" , "Failure, after initial promise" .)