ACROSS
6 BIZARRELY [small business=BIZ +, anagram: RARELY]
8 ROWAN [horse=ROAN, wide=W]
10 THAI [connection=TIE; homophone]
11 GYMNASTICS [anagram: MY + CAST + SING]
12 POLE POSITION [European=POLE, job=POSITION]
15 TANNERY [sixpence=TANNER +, end letter of the word 'only' is 'Y']
16 ABYSMAL [pit=ABYSS - son=S +, hit=LAM; reversed]
18 AMANDA REDMAN [A +, male=MAN +, lawyer=DA, embarrassed=RED +, guy=MAN]
20 DRY MARTINI [thirsty=DRY, bird=MARTIN +, one=I]
22 MALL [medium=M +, everyone=ALL]
23 FIEND [companion=FRIEND -, run=R]
24 REPLENISH [agent=REP +, author Len Deighton to give 'LEN' +, IS +, home=H]
DOWN
1 PITHY [ruth=PITY, husband=H]
2 CALIFORNIA [anagram: providing=IF +, CAROLINA]
3 FLUMMOX [female=F +, oaf=LUMMOX]
4 WONT
5 MANCUNIAN [anagram: A + MANIC + NUN]
7 ROGUE TRADERS [anagram: GET + OUR +, attackers=RAIDERS which sounds like 'RADERS']
9 DAVID BADDIEL [giant killer=DAVID, rotten=BAD +, anagram: LIED]
13 INSTALMENT [second=INSTANT, anagram: MEL]
14 MALADROIT [anagram: ADMIRAL + TO]
17 TRAINER [transport=TRAIN +, our queen=ER]
19 FLASH
21 MINE [aMbIeNcE]