Round rugby player, one tweeting regularly? (7)
I believe the answer is:
lapwing
'one tweeting regularly?' is the definition.
(lapwings are known for their calls)
'round rugby player' is the wordplay.
'round' becomes 'lap' (as in a round or lap of a park).
'rugby player' becomes 'wing' (type of rugby player).
'lap'+'wing'='LAPWING'
(Other definitions for lapwing that I've seen before include "Variety of plover" , "wader" , "Green plover" , "Plover, pewit" , "Bird of the plover family" .)