Every year locks up undesirable (6)
I believe the answer is:
pariah
'undesirable' is the definition.
(thesaurus)
'every year locks up' is the wordplay.
'every year' becomes 'pa' (per annum).
'locks' becomes 'hair' (I've seen this before).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'hair' reversed gives 'riah'.
'pa'+'riah'='PARIAH'
(Other definitions for pariah that I've seen before include "Person despised and avoided" , "Small box for valuables" , "person shunned" , "Social outcast" , "someone socially unacceptable" .)