Teased about being serious (6)
I believe the answer is:
sedate
'serious' is the definition.
(similar in meaning)
'teased about' is the wordplay.
'about' is an anagram indicator.
'teased' is an anagram of 'SEDATE'.
'being' is the link.
(Other definitions for sedate that I've seen before include "Give tranquilliser to" , "boring" , "Calm - staid" , "not disturbed by passion or excitement?" , "Calm and dignified in manner" .)