Funny dog is out endlessly barking (7)
I believe the answer is:
curious
'funny' is the definition.
(synonyms)
'dog is out endlessly barking' is the wordplay.
'dog' becomes 'cur' (cur is a kind of dog).
'endlessly' means to remove the last letter.
'barking' indicates anagramming the letters (UK slang for mad).
'is'+'out'='isout'
'isout' with its last letter removed is 'isou'.
'isou' is an anagram of 'ious'.
'cur'+'ious'='CURIOUS'
(Other definitions for curious that I've seen before include "Eager to learn, strange" , "Odd, peculiar" , "Unusual; eager to learn" , "Intrigued" , "Eager to know; strange" .)