Bonus help for the hopelessly stumped.

ACROSS

10 Doris shatters; night ends with mangled bakery ads. (9)
The answer is DAYBREAK. Doris (DAY) shatters (BREAK); night ends (daybreak)
with mangled (an anagram) bakery ads.

19 Manner in which data is sometimes displayed; remove the slang for brother from barograph. (1, 5)
The answer is A GRAPH, a manner in which data is sometimes displayed; remove the slang for
brother (BRO) from barograph--BaROgraph.

DOWN

4 Leap, defrost; soon groggy thrips gnaw the new green shoots of a season de-iced. (6, 4)
   The answer is SPRING THAW. Leap (SPRING), defrost (THAW); soon groggy thrips gnaw
(anagram of thrips gnaw) of a season (SPRING)   de-iced (THAW)

9 Mental conditions; pump up rubber tubes for water with shared H. (9)
This was a tough one for me, too! The answer is PSYCHOSES: mental condition; pump up
(PSYCH) rubber tubes for water (HOSES)  with shared H. PSYCH(h)OSES

11 Prechristian spook agency acronym? 3 Banded Italian + 1 of 7 + Caesar's 1 + Good grade. (4)
The answer is BCIA. Prehistoric (BC) spook agency (CIA). Three banded Italian (bee) + one of seven (sea)
+ Caesar's one (I) + good grade (A)