Guess cryptic clue in rush (9)
I believe the answer is:
speculate
'guess' is the definition.
(I know that guess is a more specific form of speculate)
'cryptic clue in rush' is the wordplay.
'cryptic' is an anagram indicator (a cryptic or obscure order of the letters).
'in' means one lot of letters goes inside another.
'rush' becomes 'spate' (synonyms).
'clue' is an anagram of 'ecul'.
'ecul' placed inside 'spate' is 'SPECULATE'.
(Other definitions for speculate that I've seen before include "Theorise without firm evidence" , "Conjecture, theorise" , "Make conjectures" , "Gamble - guess" , "Imagine" .)