Leader of Arab gang addicted to desert (7)
I believe the answer is:
abandon
'desert' is the definition.
(synonyms)
'leader of arab gang addicted' is the wordplay.
'leader of' suggests taking the first letters.
'gang' becomes 'band' (I've seen this in other clues).
'addicted' becomes 'on' (e.g. to be 'on' heroin).
The first letter of 'arab' is 'a'.
'a'+'band'+'on'='ABANDON'
'to' acts as a link.
(Other definitions for abandon that I've seen before include "Leave, desert" , "Lack of inhibition; desert" , "Desert; give up (action)" , "Forsake with recklessness" , "Desert or yield without restraint" .)