Recidivist regularly concealed gear under rugby player's top (10)

'recidivist' is the definition.
(synonyms)

'regularly concealed gear under rugby player's top' is the wordplay.
'regularly concealed' means one should take alternating letters (letters removed at regular intervals).
'under' means one lot of letters go next to another (below, in a down clue).
'rugby player's' becomes 'back's' (type of rugby player).
'top' becomes 'lid' (lid is a kind of top).
The alternate letters of 'gear' are 'er'.
'backs'+'lid'='backslid'
'er' put after 'backslid' is 'BACKSLIDER'.