Aware clubs are almost packed (7)
I believe the answer is:
careful
'aware' is the definition.
(thesaurus)
'clubs are almost packed' is the wordplay.
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'almost' means to remove the last letter (most of the word but not all of it).
'packed' becomes 'full' (synonyms).
'full' with its final letter taken off is 'ful'.
'c'+'are'+'ful'='CAREFUL'
(Other definitions for careful that I've seen before include "Tight-fisted" , "Attentive" , "Exercising caution" , "Thorough" , "Diligent" .)