Caught again in the shifting sand (6)
I believe the answer is:
snared
'caught' is the definition.
(snaring is a kind of catching)
'again in the shifting sand' is the wordplay.
'again' becomes 're'.
'in' means one lot of letters goes inside another.
'the shifting' is an anagram indicator.
'sand' with letters rearranged gives 'snad'.
're' placed into 'snad' is 'SNARED'.
(Other definitions for snared that I've seen before include "Caught in a trap like rabbit in noose" , "Caught in trap, maybe one with noose" , "Enticed and trapped" , "Caught in trap as by poacher" , "Trapped by sander" .)