Entertains Seamus somehow (6)
I believe the answer is:
amuses
'entertains' is the definition.
(amusing is a kind of entertaining)
'seamus somehow' is the wordplay.
'somehow' indicates an anagram.
'seamus' anagrammed gives 'AMUSES'.
(Other definitions for amuses that I've seen before include "Entertains" , "Diverts" , "provides entertainment" , "Makes (someone) laugh" .)