Trip provider needs current credentials (4)
I believe the answer is:
acid
'trip provider' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'current credentials' is the wordplay.
'current' becomes 'ac' (alternating current).
'credentials' becomes 'id' (I've seen this in other clues).
'ac'+'id'='ACID'
'needs' is the link.
Can you help me to learn more?
(Other definitions for acid that I've seen before include "Bitter - drug" , "Sour - LSD" , "It is neutralised by alkali" , "It is neutralized by alkali" , "Opposite of alkali; sour" .)