Bearing children is always painful (4)
I believe the answer is:
achy
'painful' is the definition.
(similar in meaning)
'bearing children is always' is the wordplay.
'bearing' indicates putting letters inside.
'children' becomes 'ch' (genealogical abbreviation).
'is always' becomes 'ay' (archaic term for 'always').
'ch' inserted into 'ay' is 'ACHY'.
(Other definitions for achy that I've seen before include "Pained expression" , "Needing aspirin?" , "Sore" , "Suffering minor pains" , "Feeling in need of an aspirin?" .)