Insignificant digger, it's said (5)
I believe the answer is:
minor
'insignificant' is the definition.
(similar in meaning)
'digger it's said' is the wordplay.
'digger' becomes 'miner' (I've seen this in another clue).
'it's said' indicates a 'sounds like' (homophone) clue.
'miner' sounds like 'MINOR'.
(Other definitions for minor that I've seen before include "Under-age or of little importance" , "Of small importance" , "Small-scale - child" , "Deceptively realistic (art)" , "Unimportant or unable to vote" .)