Old worker has nice new arrangement (7)
I believe the answer is:
ancient
'old' is the definition.
(similar in meaning)
'worker has nice new arrangement' is the wordplay.
'worker' becomes 'ant' (worker is a type of ant).
'has' is an insertion indicator.
'new arrangement' indicates anagramming the letters (I've seen this in other clues).
'nice' with letters rearranged gives 'ncie'.
'ant' placed around 'ncie' is 'ANCIENT'.
(Other definitions for ancient that I've seen before include "Shakespearean standard-bearer" , "Very old or belonging to times past" , "Belonging to a former age" , "showing signs of wear?" , "Archaic" .)