This puzzle has two sets of six clues. The breakthrough comes in noticing that each answer in the first set can have a double O (O2) and another letter added to it to form a word from the second set. The solutions are:
Horrifies or dismays (British) = APPALS
Front of the lower leg = SHIN
Close-knit extended family group = CLAN
What a bee might do = STING
Fitting a specific outline = SHAPED
Word to describe a concept; a name = TERM
Cafe serving light refreshments with a certain drink = TEAROOM
Cleaned hair = SHAMPOOED
Fluid used to remove heat, as from an engine = COOLANT
Guaranteed winners (hyphenated) = SHOO-INS
Reducing pain or discomfort; calming = SOOTHING
Spotted American horse breed = APPALOOSA
Since the second list is alphabetized by clue, we sort the answers by the order given in the first list:
- APPAL(OO)S(A)
- SH(OO)IN(S)
- C(OO)LAN(T)
- S(OO)T(H)ING
- SHA(M)P(OO)ED
- TE(A)R(OO)M
The letters that are neither part of the shorter words nor the double Os can be read in this order to form the solution, ASTHMA, which fits nicely with the lack of oxygen them of the puzzle.