Turn up once, oddly, with dog (5)
I believe the answer is:
occur
'turn up' is the definition.
(I've seen this before)
'once oddly with dog' is the wordplay.
'oddly' means one should take alternating letters.
'with' says to put letters next to each other.
'dog' becomes 'cur' (I've seen this before).
The alternating letters of 'once' are 'oc'.
'oc'+'cur'='OCCUR'
(Other definitions for occur that I've seen before include "Happen, transpire" , "Come to pass" , "Spring to mind" , "Turn up" , "Go on" .)