Let it stand in for an obstetrician (4)
I believe the answer is:
stet
'let it stand' is the definition.
(I've seen this before)
'in for an obstetrician' is the wordplay.
'in' indicates a hidden word.
'STET' can be found hidden inside 'for obstetrician'.
(Other definitions for stet that I've seen before include "indicates second thoughts are not always better" , "cancel amendment" , "Instruction to ignore amendment" , "Let it stand - printer's mark" , "Ignore altered material" .)