This uses extreme letters - a technique where you take the first and last letters (the 'outside' or 'extreme' letters) from specified words.
'Extremely' is the indicator telling you to take the outer letters. Look at the first and last letters of 'attritional' and 'places' - these letters spell out something that the answer hopes to conquer.
Answer: MOUNTAINEERS | 'Extremely' indicates taking outer letters - the first and last letters of 'attritional' (A,L) and 'places' (P,S) give you ALPS, which mountaineers hope to conquer.