Go by some label - a pseudonym (6)
I believe the answer is:
elapse
'go by' is the definition.
(I know that go by can be written as elapse)
'some label a pseudonym' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'ELAPSE' is hidden within 'label a pseudonym'.
(Other definitions for elapse that I've seen before include "Tick by" , "Pass away - asleep (anag)" , "Slip away" , "'Pass by, as time (6)'" , "Pass or expire - please" .)