Loose American gang round the end of town (7)
I believe the answer is:
unscrew
'loose' is the definition.
(unscrewing is a kind of loosing)
'american gang round the end of town' is the wordplay.
'american' becomes 'us'.
'gang' becomes 'crew' ('crew' can be a synonym of 'gang').
'round' means one lot of letters goes inside another.
'the end of' says to take the final letters.
The final letter of 'town' is 'n'.
'us'+'crew'='uscrew'
'uscrew' enclosing 'n' is 'UNSCREW'.
(Other definitions for unscrew that I've seen before include "Release" , "Twist and open" , "Twist off (a lid or cap)" , "Unfasten by twisting" , "Take off (eg, a lid)" .)