Overly tense and risky to catch female mythical figure (5,5)
I believe the answer is:
tooth fairy
'mythical figure' is the definition.
(the tooth fairy is an imaginary being)
'overly tense and risky to catch female' is the wordplay.
'overly tense' becomes 'toot' (I can't explain this - if you can you should believe this answer much more).
'and' means one lot of letters go next to another.
'risky' becomes 'hairy' (hairy can mean risky or dangerous).
'to catch' means one lot of letters goes inside another.
'female' becomes 'f' (abbreviation).
'hairy' going around 'f' is 'hfairy'.
'toot'+'hfairy'='TOOTH FAIRY'
(Other definitions for tooth fairy that I've seen before include "It may bring comfort to a child" , "She leaves money for molar" , "Spirit said to leave money at night in compensation for losing a gnasher" , "Parent really" , "Visitor leaving kids money" .)