Her lad became a messenger (6)
I believe the answer is:
herald
'a messenger' is the definition.
(herald is a kind of messenger)
'her lad became' is the wordplay.
'became' indicates an anagram (I've seen 'become' mean this).
'lad' is an anagram of 'ald'.
'her'+'ald'='HERALD'
(Other definitions for herald that I've seen before include "Announcer - forerunner" , "Announce, presage" , "Proclaim the approach of, like announcer of old" , "and 14: 'Hark! The -- -- sing' (carol)" , "Scottish newspaper" .)