Desire for the other bikini on vacation in pool (6)
I believe the answer is:
libido
'desire' is the definition.
(I know that libido is a type of desire)
'other bikini on vacation in pool' is the wordplay.
'other' indicates an anagram.
'on vacation' says to hollow out the word (remove centre letters) (after the inside letters have vacated the word).
'in' indicates putting letters inside.
'pool' becomes 'lido' (I've seen this before).
'bikini' with its centre taken out is 'bi'.
'bi' with letters rearranged gives 'ib'.
'ib' placed inside 'lido' is 'LIBIDO'.
'for the' acts as a link.
(Other definitions for libido that I've seen before include "Sexual impulse" , "Emotional craving" , "Freud's sex drive" , "Vital urge" , "Strong urge" .)