Run into oneself thus (4)
I believe the answer is:
ergo
'thus' is the definition.
(I've seen this before)
'run into oneself' is the wordplay.
'run' becomes 'r' (cricket abbreviation).
'into' means one lot of letters goes inside another.
'oneself' becomes 'ego'.
'r' going inside 'ego' is 'ERGO'.
(Other definitions for ergo that I've seen before include "'Cogito, ---- sum'" , "Consequently" , "for this reason" , "Thus" , "It follows" .)