Somehow, six Eels press on deadpan (14)
I believe the answer is:
expressionless
'deadpan' is the definition.
(synonyms)
'somehow six eels press on' is the wordplay.
'somehow' indicates anagramming the letters.
'six'+'eels'+'press'+'on'='sixeelspresson'
'sixeelspresson' with letters rearranged gives 'EXPRESSIONLESS'.
(Other definitions for expressionless that I've seen before include "having nothing to say" , "Deadpan" , "Betraying no emotion" , "showing no emotion" , "lost for words?" .)