Everyman 3781

[Jeceris]

Can anyone clarify:
Why communist in 18 ac "Waster, poet, communist"?
Why "run into" gives HEADED in 3 dn?
Why "severely run down" equates to LASH OUT in 4 dn?
Thank you in advance

[Lie-in King]

18a (Stephen) Spender - was one - "In 1936 he became a member of the Communist Party of Great Britain..." (Wiki)

3d Empty-headedness - 'headed' (have run; organised, in) 'empty ness (cape)'

4d Lash out (severely run down verbally) - 'la' (Fr. "the") + 'shout' (bay)

Hi Jeceris - posting the clues for those without the puzzle is always nice - sorry, I've not time to add them myself :-)