Dash briefly in B&Q, uncle's outside being surly (7)
I believe the answer is:
brusque
'surly' is the definition.
(thesaurus)
'dash briefly in bq uncle's outside' is the wordplay.
'dash briefly' becomes 'rus' (I can't explain this - if you can you should believe this answer much more).
'in' indicates putting letters inside.
'outside' means to remove the middle letters.
'uncle' with its middle taken out is 'ue'.
'rus' put within 'bq' is 'brusq'.
'brusq'+'ue'='BRUSQUE'
'being' is the link.
Can you help me to learn more?
(Other definitions for brusque that I've seen before include "Curt, blunt" , "Rudely curt" , "Curt in speech" , "Curt and offhand in manner" , "Short" .)