Very hot and humid, lacking river current (7)
I believe the answer is:
topical
'current' is the definition.
(similar in meaning)
'very hot and humid lacking river' is the wordplay.
'very hot and humid' becomes 'tropical' (I've seen this before).
'lacking' indicates named letters should be taken away.
'river' becomes 'r' (abbreviation for river).
'tropical' with 'r' taken away is 'TOPICAL'.
(Other definitions for topical that I've seen before include "Of interest at the present time" , "Of local interest" , "In the news" , "like this newspaper" , "Having reference to current events" .)