It's tiresome wandering outside (7)
I believe the answer is:
tedious
'it's tiresome' is the definition.
(synonyms)
'wandering outside' is the wordplay.
'wandering' is an anagram indicator.
'outside' with letters rearranged gives 'TEDIOUS'.
(Other definitions for tedious that I've seen before include "Wearisome, boring" , "not exciting" , "Boring, monotonous" , "Outside (anag.)" , "Long, slow, dull" .)